INDUSTRIAL POISONING
FROM FUMES, GASES AND POISONS OF MANUFACTURING PROCESSES
BY THE SAME AUTHOR
LEAD POISONING AND LEAD ABSORPTION:
THE SYMPTOMS, PATHOLOGY AND PREVENTION, WITH SPECIAL REFERENCE
TO THEIR INDUSTRIAL ORIGIN AND AN ACCOUNT OF THE PRINCIPAL
PROCESSES INVOLVING RISK.
By THOMAS M. LEGGE M.D. (Oxon.), D.P.H. (Cantab.), H.M. Medical
Inspector of Factories; Lecturer on Factory Hygiene, University
of Manchester; and KENNETH W. GOADBY, D.P.H. (Cantab.),
Pathologist and Lecturer on Bacteriology, National Dental
Hospital. Illustrated. viii+308 pp. 12s. 6_d._ net.
LONDON: EDWARD ARNOLD.
INDUSTRIAL POISONING
FROM FUMES, GASES AND POISONS
OF MANUFACTURING PROCESSES
BY
DR. J. RAMBOUSEK
PROFESSOR OF FACTORY HYGIENE,
AND CHIEF STATE HEALTH OFFICER, PRAGUE
TRANSLATED AND EDITED BY
THOMAS M. LEGGE, M.D., D.P.H.
H.M. MEDICAL INSPECTOR OF FACTORIES
JOINT AUTHOR OF ‘LEAD POISONING AND LEAD ABSORPTION’
WITH ILLUSTRATIONS
LONDON
EDWARD ARNOLD
1913
TRANSLATOR’S PREFACE
I undertook the translation of Dr. Rambousek’s book because it seemed to
me to treat the subject of industrial poisons in as novel, comprehensive,
and systematic a manner as was possible within the compass of a single
volume. Having learnt much myself from Continental writings on industrial
diseases and factory hygiene, I was anxious to let others also see how
wide a field they had covered and how thorough were the regulations for
dangerous trades abroad, especially in Germany. A praiseworthy feature of
Dr. Rambousek’s book was the wealth of references to the work of foreign
writers which is made on almost every page. To have left these names
and references, however, in the text as he has done would have made the
translation tedious reading, and therefore for the sake of those who
desire to pursue inquiry further I have adopted the course of collecting
the great majority and placing them all together in an appendix at the
end of the volume.
Dr. Rambousek as a medical man, a chemist, and a government official
having control of industrial matters, is equipped with the very special
knowledge required to describe the manufacturing processes giving rise
to injurious effects, the pathology of the lesions set up, and the
preventive measures necessary to combat them. In his references to work
done in this country he has relied largely on abstracts which have
appeared in medical and technical journals published on the Continent. I
have only thought it necessary to amplify his statements when important
work carried out here on industrial poisoning,—such as that on nickel
carbonyl and on ferro-silicon—had been insufficiently noted. Such
additions are introduced in square brackets or in footnotes.
In his preface Dr. Rambousek says ‘the book is intended for all who
are, or are obliged to be, or ought to be, interested in industrial
poisoning.’ No words could better describe the scope of the book.
The work of translation would never have been begun but for the
assistance given me in Parts II and III by my sister, Miss H. Edith
Legge. To her, and to Mr. H. E. Brothers, F.I.C., who has been to the
trouble of reading the proofs and correcting many mistakes which my
technical knowledge was insufficient to enable me to detect, my best
thanks are due.
I am indebted to Messrs. Davidson & Co., Belfast, for permission to use
figs. 46 and 48; to Messrs. Locke, Lancaster & Co., Millwall, for fig.
27; to Mr. R. Jacobson, for figs. 30, 33, 37, 38, and 43; to Messrs.
Siebe, Gorman & Co., for figs. 32, 39, and 40; to Messrs. Blackman & Co.
for fig. 47; to Messrs. Matthews & Yates for fig. 54; to H.M. Controller
of the Stationery Office for permission to reproduce figs. 52, 53, and
54, and the diagrams on p. 284; and lastly to my publisher, for figs. 41,
42, 43, and 49, which are taken from the book by Dr. K. W. Goadby and
myself on ‘Lead Poisoning and Lead Absorption.’
T. M. L.
HAMPSTEAD, _May 1913_.
CONTENTS
PAGE
INTRODUCTION xiii
Part I.—Description of the industries and processes attended
with risk of poisoning: incidence of such poisoning
CHEMICAL INDUSTRY 1
Sulphuric acid industry (sulphur dioxide): use of sulphuric acid 4
Its effects on health 9
Hydrochloric acid, saltcake and soda industry 14
Their effects on health 20
Use of sulphate and sulphide of soda 22
Ultramarine 22
Sulphonal 22
Diethyl sulphate 23
Chlorine, chloride of lime and chlorates 23
Their effect on health 26
Other chlorine compounds and their use as well as bromine,
iodine and fluorine 29
Chlorides of phosphorus 30
Chlorides of sulphur 31
Zinc chloride 32
Rock salt 32
Organic chlorine compounds 32
Carbon oxychloride (phosgene) 32
Carbon chlorine compounds (aliphatic) 33
Methyl chloride 33
Methylene chloride 34
Carbon tetrachloride 34
Ethyl chloride 34
Monochloracetic acid 34
Chloral 34
Chloroform 34
Chloride of nitrogen 35
Cyanogen chloride 35
Chlorobenzene 35
Benzo trichloride, benzyl chloride 35
Nitro- and dinitro-chlorobenzene 35
Iodine and iodine compounds 36
Bromine and bromine compounds 36
Methyl iodide and methyl bromide 36
Fluorine compounds 37
Hydrofluoric and silicofluoric acids 38
Manufacture and uses of nitric acid 39
Its effect on health 40
Nitric and nitrous salts and compounds 44
Barium nitrate 44
Ammonium nitrate 44
Lead nitrate 44
Mercurous and mercuric nitrate 44
Silver nitrate 45
Sodium nitrite 45
Amyl nitrite 45
Manufacture of explosives and their effects 45
Fulminate of mercury 46
Nitro-glycerin 46
Dynamite 47
Gun cotton 48
Collodion cotton, smokeless powder 48
Manufacture of phosphorus and lucifer matches and their effects 49
Other uses of phosphorus and compounds of phosphorus 52
Phosphor-bronze 52
Sulphide of phosphorus 52
Phosphoretted hydrogen 52
Superphosphate and artificial manure 53
Basic slag 54
Chromium compounds and their uses 55
Sodium and potassium bichromate 55
Lead chromate and chrome colours 55
Their effect on health 56
Manganese compounds and their effects 58
Mineral oil industry and the use of petroleum and benzine 59
Chemical cleaning 61
Their effect on health 61
Recovery and use of sulphur 64
Its effect on health 65
Sulphuretted hydrogen and its effect 65
Preparation and use of carbon bisulphide in vulcanising, &c. 68
Its effect on health 69
Preparation of illuminating gas 71
Its effect on health 74
Coke ovens and risk from them 77
Other kinds of power and illuminating gas 80
Producer gas 80
Blast furnace gas 82
Water gas 82
Dowson and Mond gas 82
Suction gas 83
Acetylene (calcium carbide) 85
Their effect on health 87
Ammonia and ammonium compounds 90
Use of ammonia and its effects 92
Cyanogen compounds 93
Use of cyanide, and their effects 95
Coal tar and tar products 96
Their effects on health 101
Artificial organic dye stuffs (coal tar colours) 107
Their effects on health 112
RECOVERY AND USE OF METALS 120
Lead poisoning in general 120
Lead, silver and zinc smelting 122
Spelter works 125
Lead poisoning in lead smelting and spelter works 126
White lead and other use of lead colours 131
Lead poisoning in the manufacture and use of white lead
and lead paints 132
Manufacture of electric accumulators 134
The ceramic industry 135
Coarse ware pottery 136
Manufacture of stove tiles 137
Stoneware and porcelain 138
Lead poisoning in letterpress printing 138
Lead poisoning in filecutting, polishing precious stones,
musical instrument making, &c. 140
Mercury (poisoning in its recovery and use) 141
Mercurial poisoning in water-gilding, coating mirrors, in
felt hat making, &c. 142
Arsenic (poisoning in its recovery and in use of arsenic and
arsenic compounds) 143
Recovery of arsenic and white arsenic 143
Poisoning by arseniuretted hydrogen gas 145
Antimony 146
Extraction of iron 146
Ferro-silicon 149
Zinc 151
Copper, brass (brassfounders’ ague) 151
Metal pickling 152
OTHER INDUSTRIES 153
Treatment of stone and earths; lime burning, glass 153
Treatment of animal products 154
Preparation of vegetable foodstuffs 154
Poisonous woods 154
Textile industry 156
Part II.—Pathology and treatment of industrial poisoning
INDUSTRIAL POISONS IN GENERAL 157
Channels of absorption, classification, susceptibility,
immunity 158
Fate of poisons in the body—absorption, cumulative action,
excretion 162
General remarks on treatment 163
INDUSTRIAL POISONS IN PARTICULAR 169
Group: mineral acids, halogens, inorganic halogen compounds,
alkalis 169
Hydrochloric acid 170
Hydrofluoric and silico-fluoric acids 171
Sulphur dioxide and sulphuric acid 171
Nitrous fumes, nitric acid 172
Chlorine, bromine, iodine 173
Chlorides of phosphorus, sulphur and zinc 174
Ammonia 175
Alkalis 176
Group: Metals and metal-compounds 176
Lead and its compounds 177
Zinc and its alloys 182
Mercury and its compounds 183
Manganese and its compounds 184
Chromium and its compounds 185
Nickel salts (nickel carbonyl) 186
Copper 188
Silver and its compounds 188
Group: Arsenic, Phosphorus 189
Arsenic and its oxides 189
Phosphorus 190
Phosphoretted hydrogen 191
Group: Sulphuretted hydrogen, carbon bisulphide, and cyanogen
(nerve poisons) 192
Sulphuretted hydrogen 192
Carbon bisulphide 193
Cyanogen compounds 195
Group: Arseniuretted hydrogen and carbonic oxide (blood
poisons) 197
Group: Hydrocarbons of the aliphatic and aromatic series and
their halogen and hydroxyl substitution products 202
Sub-group: Hydrocarbons of mineral oils and their distillation
products (benzine, paraffin, &c.) 202
Sub-group: Hydrocarbons of the aromatic series 204
Benzene and its homologues 204
Naphthalene 208
Sub-group: Halogen substitution products of the aliphatic
series (narcotic poisons) 208
Sub-group: Halogen substitution products of the benzene
series 209
Sub-group: Hydroxyl substitution products of the fatty
series 210
Group: Nitro- and amido-derivatives of the aliphatic and
aromatic series 211
Sub-group: Nitro-derivatives of the aliphatic series 212
Sub-group: Nitro- and amido-derivatives of the aromatic
series 212
Turpentine, pyridene, alkaloids, nicotine, poisonous woods 215
Part III.—Preventive measures against industrial poisoning
GENERAL PREVENTIVE MEASURES 217
International action, notification of poisoning, schedules
of poisons 218
Special preventive measures for workers—selection, periodical
medical examination, co-operation of workers, &c. 226
Rescue appliances 230
Washing accommodation and baths 237
Removal of dust and fumes by exhaust ventilation 242
PREVENTIVE MEASURES IN PARTICULAR INDUSTRIES 256
Sulphuric acid industry 256
Hydrochloric acid and soda industries 257
Chlorine, bleaching powder, chlorine compounds 259
Manufacture of nitric acid and explosives 260
Artificial manures, basic slag 261
Chromium and its compounds 265
Petroleum, benzine 267
Phosphorus, lucifer matches 268
Bisulphide of carbon 271
Illuminating gas, tar production 275
Gas power plant 276
Acetylene gas installations 278
Ammonia 279
Cyanogen, cyanogen compounds 280
Coal tar, tar products 280
Organic dye-stuffs, coal tar colours 285
Recovery and use of metals 288
Iron 289
Lead 292
Lead smelting 299
Electric accumulators 305
White lead and lead colours 310
Letterpress printing 316
Ceramic industry 319
File cutting 321
Other uses of lead 322
Zinc smelting 323
Brass casting, metal pickling 325
Recovery and use of mercury 326
Arsenic and its compounds 328
Gold and silver 329
PREVENTIVE MEASURES IN OTHER TRADES 329
Manufacture and use of varnishes 330
Production of vegetable foods 332
Wood working 335
Paper manufacture 336
Textile industries 336
APPENDIX 339
INDEX 355
INTRODUCTION
The attempt to systematise from the scientific standpoint the mass of
material that has been collected about poisons is a very heavy task, even
for the toxicologist who desires to treat his subject comprehensively.
How much greater is the difficulty of writing a systematic book on
industrial poisoning keeping practical application in the forefront!
Technical considerations which are decisive in the causation and
prevention of industrial poisoning are here of especial moment, and must
naturally influence classification of the subject-matter when the object
is to assist those concerned in factory hygiene.
Bearing this in mind, I have divided the subject into three parts. The
arrangement of the first, which gives as complete a statement as possible
of the occurrence of industrial poisoning, into industries and processes
was determined on technical grounds. The second, which amplifies the
first, attempts to summarise the pathology or symptoms of the various
forms of poisoning. The references to the literature of the particular
subjects—as exhaustive as I could make them—will lighten further study.
To these two parts, following on knowledge of causation and symptoms, the
third, in which preventive measures are outlined, is linked.
The apparent drawback in use of the book is that one form of poisoning
has often to be referred to in three places. But, I hope, this is more
than counterbalanced by the completeness of the scheme which results from
the subdivision of the subject.
The pathology of industrial poisoning necessitates frequent repetition
when describing the branches of industry giving rise to the
intoxication, as one and the same form can occur in the most varied
processes. The numerous instances of actual cases of poisoning quoted
must therefore be regarded as conforming to the same pathological type.
Similarly, preventive measures require separate systematic treatment in
order to avoid constant repetition which would otherwise obscure the
general survey. Quite a number of means of prevention apply equally
to several industries in which the same cause is at work. The success
attained by thus simplifying the issues is the greater because such
common measures are the easier to carry through and to supervise.
The method therefore has been adopted only after serious reflection and
has been directed mainly by practical considerations.
Recent cases which have either been reported or come to the knowledge
of the author have been given, with particulars as exact as possible.
Cases dating back some time have been omitted intentionally so as to
exclude everything which did not correspond with the present conditions
of industry and trade. Historical facts only receive consideration in so
far as they are fundamentally important and necessary for the sake of
completeness.
The details given in Part I of actual instances will supply material for
fresh efforts, renewed investigation, and new points of attack.
INDUSTRIAL POISONING
PART I
_DESCRIPTION OF THE INDUSTRIES AND PROCESSES ATTENDED WITH RISK OF
POISONING; INCIDENCE OF SUCH POISONING_
I. THE CHEMICAL INDUSTRY
GENERAL CONSIDERATIONS AS TO INCIDENCE OF INDUSTRIAL POISONING
The chemical industry offers naturally a wide field for the occurrence of
industrial poisoning. Daily contact with the actual poisonous substances
to be prepared, used, stored, and despatched in large quantity gives
opportunity for either acute or chronic poisoning—in the former case
from sudden accidental entrance into the system of fairly large doses,
as the result of defective or careless manipulation, and, in the latter,
constant gradual absorption (often unsuspected) of the poison in small
amount.
The industry, however, can take credit for the way in which incidence
of industrial poisoning has been kept down in view of the magnitude and
variety of the risks which often threaten. This is attributable to the
comprehensive hygienic measures enforced in large chemical works keeping
abreast of modern advance in technical knowledge. A section of this
book deals with the principles underlying these measures. Nevertheless,
despite all regulations, risk of poisoning cannot be wholly banished.
Again and again accidents and illness occur for which industrial
poisoning is responsible. Wholly to prevent this is as impossible as
entirely to prevent accidents by mechanical guarding of machinery.
Owing to the unknown sources of danger, successful measures to ward it
off are often difficult. The rapid advance of this branch of industry,
the constant development of new processes and reactions, the frequent
discovery of new materials (with properties at first unknown, and for a
long time insufficiently understood, but nevertheless indispensable),
constantly give rise to new dangers and possibilities of danger, of which
an accident or some disease with hitherto unknown symptoms is the first
indication. Further, even when the dangerous effects are recognised,
there may often be difficulty in devising appropriate precautions, as
circumstances may prevent immediate recognition of the action of the
poison. We cannot always tell, for instance, with the substances used
or produced in the processes, which is responsible for the poisoning,
because, not infrequently, the substances in question are not chemically
pure, but may be either raw products, bye-products, &c., producing
mixtures of different bodies or liberating different chemical compounds
as impurities.
Hence difficulty often arises in the strict scientific explanation
of particular cases of poisoning, and, in a text-book such as this,
difficulty also of description. A rather full treatment of the technical
processes may make the task easier and help to give a connected picture
of the risks of poisoning in the chemical industry. Such a procedure may
be especially useful to readers insufficiently acquainted with chemical
technology.
We are indebted to Leymann[1] and Grandhomme[2] especially for knowledge
of incidence of industrial poisoning in this industry. The statistical
data furnished by them are the most important proof that poisoning, at
any rate in large factories, is not of very frequent occurrence.
Leymann’s statistics relate to a large modern works in which the number
employed during the twenty-three years of observation increased from
640 in the year 1891 to 1562 in 1904, giving an average of about 1000
yearly, one-half of whom might properly be defined as ‘chemical workers.’
The factory is concerned in the manufacture of sulphuric, nitric, and
hydrochloric acids, alkali, bichromates, aniline, trinitro-phenol,
bleaching powder, organic chlorine compounds, and potassium permanganate.
These statistics are usefully complemented by those of Grandhomme drawn
from the colour works at Höchst a-M. This large aniline works employs
from 2600 to 2700 workers; the raw materials are principally benzene and
its homologues, naphthalene and anthracene. The manufacture includes the
production of coal-tar colours, nitro- and dinitro-benzene, aniline,
rosaniline, fuchsine, and other aniline colours, and finally such
pharmaceutical preparations as antipyrin, dermatol, sanoform, &c. Of the
2700 employed, 1400 are chemical workers and the remainder labourers.
These two series of statistics based on exact observations and covering
allied chemical manufacture are taken together. They seek to give the
answer to the question—How many and what industrial poisonings are found?
The figures of Leymann (on an average of 1000 workers employed per annum)
show 285 cases of poisoning reported between the years 1881 and 1904. Of
these 275 were caused by aniline, toluidine, nitro- and dinitro-benzene,
nitrophenol, nitrochloro and dinitrochloro benzene. Three were fatal
and several involved lengthy invalidity (from 30 to 134 days, owing to
secondary pneumonia). Included further are one severe case of chrome
(bichromate) poisoning (with nephritis as a sequela), five cases of lead
poisoning, three of chlorine, and one of sulphuretted hydrogen gas. In
the Höchst a-M. factory (employing about 2500 workers) there were, in the
ten years 1883-92, only 129 cases of poisoning, of which 109 were due to
aniline. Later figures for the years 1893-5 showed 122 cases, of which 43
were due to aniline and 76 to lead (contracted mostly in the nitrating
house). Grandhomme mentions further hyperidrosis among persons employed
on solutions of calcium chloride, injury to health from inhalation of
methyl iodide vapour in the antipyrin department, a fatal case of benzene
poisoning (entering an empty vessel in which materials had previously
been extracted with benzene), and finally ulceration and perforation of
the septum of the nose in several chrome workers.
The number of severe cases is not large, but it must be remembered that
the factories to which the figures relate are in every respect models
of their kind, amply provided with safety appliances and arrangements
for the welfare of the workers. The relatively small amount of poisoning
is to be attributed without doubt to the precautionary measures taken.
Further, in the statistics referred to only those cases are included
in which the symptoms were definite, or so severe as to necessitate
medical treatment. Absorption of the poison in small amount without
producing characteristic symptoms, as is often the case with irritating
or corrosive fumes, and such as involve only temporary indisposition, are
not included. Leymann himself refers to this when dealing with illness
observed in the mineral acid department (especially sulphuric acid), and
calls attention to the frequency of affections of the respiratory organs
among the persons employed, attributing them rightly to the irritating
and corrosive effect of the acid vapour. Elsewhere he refers to the
frequency of digestive disturbance among persons coming into contact
with sodium sulphide, and thinks that this may be due to the action of
sulphuretted hydrogen gas.
Nevertheless, the effect of industrial poisons on the health of workers
in chemical factories ought on no account to be made light of. The
admirable results cited are due to a proper recognition of the danger,
with consequent care to guard against it. Not only have Grandhomme
and Leymann[A] rendered great services by their work, but the firms
in question also, by allowing such full and careful inquiries to be
undertaken and published.
SULPHURIC ACID (SULPHUR DIOXIDE)
MANUFACTURE.—Sulphur dioxide, generally obtained by roasting pyrites in
furnaces of various constructions, or, more rarely, by burning brimstone
or sulphur from the spent oxide of gas-works, serves as the raw material
for the manufacture of sulphuric acid. Before roasting the pyrites is
crushed, the ‘lump ore’ then separated from the ‘smalls,’ the former
roasted in ‘lump-burners’ or kilns (generally several roasting furnace
hearths united into one system), and the latter preferably in Malétra and
Malétra-Schaffner shelf-burners (fig. 1) composed of several superimposed
firebrick shelves. The pyrites is charged on to the uppermost shelf and
gradually worked downwards. Pyrites residues are not suitable for direct
recovery of iron, but copper can be recovered from residues sufficiently
rich in metal by the wet process; the residues thus freed of copper and
sulphur are then smelted for recovery of iron.
[Illustration: FIG. 1.—Pyrites Burner for Smalls (_after Lueger_)]
Utilisation for sulphuric acid manufacture of the sulphur dioxide given
off in the calcining of zinc blende (see Spelter works), impracticable in
reverberatory furnaces, has been made possible at the Rhenania factory by
introduction of muffle furnaces (several superimposed), because by this
means the gases led off are sufficiently concentrated, as they are not
diluted with the gases and smoke from the heating fires. This method,
like any other which utilises the gases from roasting furnaces, has
great hygienic, in addition to economical, advantages, because escape
of sulphur dioxide gas is avoided. Furnace gases, too poor in sulphur
dioxide to serve for direct production of sulphuric acid, can with
advantage be made to produce liquid anhydrous sulphur dioxide. Thus, the
sulphur dioxide gas from the furnaces is first absorbed by water, driven
off again by boiling, cooled, dried, and liquefied by pressure.
The gaseous sulphur dioxide obtained by any of the methods described is
converted into sulphuric acid either by (_a_) the chamber process or
(_b_) the contact process.
In the _lead chamber process_ the furnace gases pass through flues in
which the flue dust and a portion of the arsenious acid are deposited
into the Glover tower at a temperature of about 300° C., and from there
into the lead chambers where oxidation of the sulphur dioxide into
sulphuric acid takes place, in the presence of sufficient water, by
transference of the oxygen of the air through the intervention of the
oxides of nitrogen. The gases containing oxides of nitrogen, &c., which
are drawn out of the lead chambers, have the nitrous fumes absorbed
in the Gay-Lussac tower (of which there are one or two in series), by
passage through sulphuric acid which is made to trickle down the tower.
The sulphuric acid so obtained, rich in oxides of nitrogen, and the
chamber acid are led to the Glover tower for the purpose of denitration
and concentration, so that all the sulphuric acid leaves the Glover
as Glover acid of about 136-144° Tw. Losses in nitrous fumes are best
made up by addition of nitric acid at the Glover or introduction into
the first chamber. The deficiency is also frequently made good from
nitre-pots.
The lead chambers (fig. 2) are usually constructed entirely—sides,
roof, and floor—of lead sheets, which are joined together by means of a
hydrogen blowpipe. The sheets forming the roof and walls are supported,
independent of the bottom, on a framework of wood. The capacity varies
from 35,000 to 80,000 cubic feet. The floor forms a flat collecting
surface for the chamber acid which lutes the chamber from the outer air.
The necessary water is introduced into the chamber as steam or fine water
spray.
The Glover and Gay-Lussac towers are lead towers. The Glover is lined
with acid-proof bricks and filled with acid-proof packing to increase
the amount of contact. The Gay-Lussac is filled with coke over which
the concentrated sulphuric acid referred to above flows, forming, after
absorption of the nitrous fumes, nitro-sulphuric acid.
[Illustration: FIG. 2A.—Lead Chamber System—Section through X X (_after
Ost_)
FIG. 2B.—Lead Chamber System—Plan
A Pyrites Burner
B Glover Tower
C Draft Regulator
D, D´ Lead Chambers
E Air Shaft
F, F,´ F,´´ F´´´ Acid Reservoirs
G Acid Egg
H Cooler
J Gay-Lussac Tower]
As already stated, two Gay-Lussac towers are usually connected together,
or where there are several lead-chamber systems there is, apart from the
Gay-Lussac attached to each, a central Gay-Lussac in addition, common
to the whole series. The introduction of several Gay-Lussac towers
has the advantage of preventing loss of the nitrous fumes as much as
possible—mainly on economical grounds, as nitric acid is expensive. But
this arrangement is at the same time advantageous on hygienic grounds, as
escape of poisonous gases containing nitrous fumes, &c., is effectually
avoided. The acids are driven to the top of the towers by compressed air.
The whole system—chambers and towers—is connected by means of wide lead
conduits. Frequently, for the purpose of quickening the chamber process
(by increasing the number of condensing surfaces) Lunge-Rohrmann plate
towers are inserted in the system—tall towers lined with lead in which
square perforated plates are hung horizontally, and down which diluted
sulphuric acid trickles.
To increase the draught in the whole system a chimney is usual at
the end, and, in addition, a fan of hard lead or earthenware may be
introduced in front of the first chamber or between the two Gay-Lussac
towers. Maintenance of a constant uniform draught is not only necessary
for technical reasons, but has hygienic interest, since escape of
injurious gases is avoided (see also Part III).
The chamber acid (of 110°-120° Tw. = 63-70 %) and the stronger Glover
acid (of 136°-144° Tw. = 75-82 %) contain impurities. In order to obtain
for certain purposes pure strong acid the chamber acid is purified and
concentrated. The impurities are notably arsenious and nitrous acids
(Glover acid is N free), lead, copper, and iron. Concentration (apart
from that to Glover acid in the Glover tower) is effected by evaporation
in lead pans to 140° Tw. and finally in glass balloons or platinum stills
to 168° Tw. (= 97 %). The lead pans are generally heated by utilising the
waste heat from the furnaces or by steam coils in the acid itself, or
even by direct firing.
Production of sulphuric acid by the _contact method_ depends on the fact
that a mixture of sulphur dioxide and excess of oxygen (air) combines
to form sulphur trioxide at a moderate heat in presence of a contact
substance such as platinised asbestos or oxide of iron. The sulphur
dioxide must be carefully cleaned and dried, and with the excess of air
is passed through the contact substance. If asbestos carrying a small
percentage of finely divided platinum is the contact substance, it is
generally used in the form of pipes; oxide of iron (the residue of
pyrites), if used, is charged into a furnace. Cooling by a coil of pipes
and condensation in washing towers supplied with concentrated sulphuric
acid always forms a part of the process. A fan draws the gases from the
roasting furnaces and drives them through the system. The end product
is a fuming sulphuric acid containing 20-30 per cent. SO₃. From this by
distillation a concentrated acid and a pure anhydride are obtained. From
a health point of view it is of importance to know that all sulphuric
acid derived from this anhydride is pure and free from arsenic.
The most important _uses_ of sulphuric acid are the following: as chamber
acid (110°-120° Tw.) in the superphosphate, ammonium sulphate, and alum
industries; as Glover acid (140°-150° Tw.) in the Leblanc process, i.e.
saltcake and manufacture of hydrochloric acid, and to etch metals; as
sulphuric acid of 168° Tw. in colour and explosives manufacture (nitric
acid, nitro-benzene, nitro-glycerine, gun-cotton, &c.); as concentrated
sulphuric acid and anhydride for the production of organic sulphonic
acids (for the alizarin and naphthol industry) and in the refining of
petroleum and other oils. Completely de-arsenicated sulphuric acid
is used in making starch, sugar, pharmaceutical preparations, and in
electrical accumulator manufacture.
EFFECTS ON HEALTH.—The health of sulphuric acid workers cannot in general
be described as unfavourable.
In comparison with chemical workers they have, it is said, relatively
the lowest morbidity. Although in this industrial occupation no
special factors are at work which injure in general the health of the
workers, there is a characteristic effect, without doubt due to the
occupation—namely, disease of the respiratory organs. Leymann’s figures
are sufficiently large to show that the number of cases of diseases
of the respiratory organs is decidedly greater in the sulphuric acid
industry than among other chemical workers. He attributes this to the
irritating and corrosive effect of sulphur dioxide and sulphuric acid
vapour on the mucous membrane of the respiratory tract, as inhalation
of these gases can never be quite avoided, because the draught in the
furnace and chamber system varies, and the working is not always uniform.
Strongly irritating vapours escape again in making a high percentage
acid in platinum vessels, which in consequence are difficult to keep
air-tight. Of greater importance than these injurious effects from
frequent inhalation of small quantities of acid vapours, or employment
in workrooms in which the air is slightly charged with acid, is the
accidental sudden inhalation of large quantities of acid gases, which may
arise in the manufacture, especially by careless attendance. Formerly
this was common in charging the roasting furnaces when the draught in the
furnace, on addition of the pyrites, was not strengthened at the same
time. This can be easily avoided by artificial regulation of the draught.
Accidents through inhalation of acid gases occur further when entering
the lead chambers or acid tanks, and in emptying the towers. Heinzerling
relates several cases taken from factory inspectors’ reports. Thus, in a
sulphuric acid factory the deposit (lead oxysulphate) which had collected
on the floor of a chamber was being removed: to effect this the lead
chambers were opened at the side. Two of the workers, who had probably
been exposed too long to the acid vapours evolved in stirring up the
deposit, died a short time after they had finished the work. A similar
fatality occurred in cleaning out a nitro-sulphuric acid tank, the
required neutralisation of the acid by lime before entering having been
omitted. Of the two workers who entered, one died the next day; the other
remained unaffected. The deceased had, as the post mortem showed, already
suffered previously from pleurisy. A fatality from breathing nitrous
fumes is described fully in the report of the Union of Chemical Industry
for the year 1905. The worker was engaged with two others in fixing a fan
to a lead chamber; the workers omitted to wait for the arrival of the
foreman who was to have supervised the operation. Although the men used
moist sponges as respirators, one of them inhaled nitrous fumes escaping
from the chamber in such quantity that he died the following day.
Similar accidents have occurred in cleaning out the Gay-Lussac towers.
Such poisonings have repeatedly occurred in Germany. Fatal poisoning is
recorded in the report of the Union of Chemical Industry, in the emptying
and cleaning of a Gay-Lussac tower despite careful precautions. The
tower, filled with coke, had been previously well washed with water, and
during the operation of emptying, air had been constantly blown through
by means of a Körting’s injector. The affected worker had been in the
tower about an hour; two hours later symptoms of poisoning set in which
proved fatal in an hour despite immediate medical attention. As such
accidents kept on recurring, the Union of Chemical Industry drew up
special precautions to be adopted in the emptying of these towers, which
are printed in Part III.
Naturally, in all these cases it is difficult to say exactly which of the
acid gases arising in the production of sulphuric acid was responsible
for the poisoning. In the fatal cases cited, probably nitrous fumes
played the more important part.
Poisoning has occurred in the transport of sulphuric acid. In some of
the cases, at all events, gaseous impurities, especially arseniuretted
hydrogen, were present.
Thus, in the reports of the German Union of Chemical Industry for the
year 1901, a worker succumbed through inhalation of poisonous gases in
cleaning out a tank waggon for the transport of sulphuric acid. The tank
was cleaned of the adhering mud, as had been the custom for years, by a
man who climbed into it. No injurious effects had been noted previously
at the work, and no further precautions were taken than that one worker
relieved another at short intervals, and the work was carried on under
supervision. On the occasion in question, however, there was an unusually
large quantity of deposit, although the quality of the sulphuric acid was
the same, and work had to be continued longer. The worker who remained
longest in the tank became ill on his way home and died in hospital
the following day; the other workers were only slightly affected. The
sulphuric acid used by the firm in question immediately before the
accident came from a newly built factory in which anhydrous sulphuric
acid had been prepared by a special process. The acid was Glover acid,
and it is possible that selenium and arsenic compounds were present
in the residues. Arseniuretted hydrogen might have been generated in
digging up the mud. Two similar fatalities are described in the report of
the same Union for the year 1905. They happened similarly in cleaning out
a sulphuric acid tank waggon, and in them the arsenic in the acid was the
cause. Preliminary swilling out with water diluted the remainder of the
sulphuric acid, but, nevertheless, it acted on the iron of the container.
Generation of hydrogen gas is the condition for the reduction of the
arsenious acid present in sulphuric acid with formation of arseniuretted
hydrogen. In portions of the viscera arsenic was found. Lately in the
annual reports of the Union of Chemical Industry for 1908 several cases
of poisoning are described which were caused by sulphuric acid. A worker
took a sample out of a vessel of sulphuric acid containing sulphuretted
hydrogen gas. Instead of using the prescribed cock, he opened the
man-hole and put his head inside, inhaling concentrated sulphuretted
hydrogen gas. He became immediately unconscious and died. Through
ignorance no use was made of the oxygen apparatus.
Another fatality occurred through a foreman directing some workers,
contrary to the regulations against accidents from nitrous gases, to
clean a vessel containing nitric and sulphuric acids. They wore no air
helmets: one died shortly after from inhalation of nitrous fumes. Under
certain circumstances even the breaking of carboys filled with sulphuric
acid may give rise to severe poisoning through inhalation of acid gases.
Thus a fatality[1] occurred to the occupier of a workroom next some
premises in which sulphuric acid carboys had been accidentally broken.
Severe symptoms developed the same night, and he succumbed the next
morning in spite of treatment with oxygen. A worker in the factory became
seriously ill but recovered.
A similar case is described[2] in a factory where concentrated sulphuric
acid had been spilt. The workers covered the spot with shavings,
which resulted in strong development of sulphur dioxide, leading to
unconsciousness in one worker.
The frequent observation of the injurious effect of acid gases on the
teeth of workers requires mention; inflammation of the eyes of workers
also is attributed to the effects of sulphuric acid.
Leymann’s statistics show _corrosions and burns_ among sulphuric acid
workers to be more than five times that among other classes. Such burns
happen most frequently from carelessness. Thus, in the reports of the
Union of Chemical Industry for 1901, three severe accidents are mentioned
which occurred from use of compressed air. In two cases the acid had been
introduced before the compressed air had been turned off; in the third
the worker let the compressed air into the vessel and forgot to turn off
the inlet valve. Although the valves were provided with lead guards,
some of the acid squirted into the worker’s face. In one case complete
blindness followed, in a second blindness in one eye, and in the third
blindness in one eye and impaired vision of the other.
Besides these dangers from the raw material, bye-products, and products
of the manufacture, _lead poisoning_ has been reported in the erection
and repair of lead chambers. The lead burners generally use a hydrogen
flame; the necessary hydrogen is usually made from zinc and sulphuric
acid and is led to the iron by a tube. If the zinc and sulphuric acid
contain arsenic, the very dangerous arseniuretted hydrogen is formed,
which escapes through leakages in the piping, or is burnt in the flame to
arsenious acid.
Further, the lead burners and plumbers are exposed to the danger of
chronic lead poisoning from insufficient observance of the personal
precautionary measures necessary to guard against it (see Part III).
Those who are constantly engaged in burning the lead sheets and pipes of
the chambers suffer not infrequently from severe symptoms. Unfortunately,
the work requires skill and experience, and hence alternation of
employment is hardly possible.
Finally, mention should be made of poisoning by _arseniuretted hydrogen
gas_ from vessels filled with sulphuric acid containing arsenic as an
impurity, and by sulphuretted hydrogen gas in purifying the acid itself.
In the manufacture of liquid _sulphur dioxide_, injury to health can
arise from inhalation of the acid escaping from the apparatus. The most
frequent cause for such escape of sulphur dioxide is erosion of the walls
of the compressor pumps and of the transport vessels, in consequence of
the gas being insufficiently dried, as, when moist, it attacks iron.
Sulphur dioxide will come up for further consideration when describing
the industrial processes giving rise to it, or in which it is used.
HYDROCHLORIC ACID, SALTCAKE, AND SODA
MANUFACTURE.—The production of hydrochloric acid (HCl), sodium sulphate
(Na₂SO₄), and sodium sulphide (Na₂S) forms part of the manufacture of
soda (Na₂CO₃) by the Leblanc process. The products first named increase
in importance, while the Leblanc soda process is being replaced more and
more by the manufacture of soda by the Solvay ammonia process, so much so
that on the Continent the latter method predominates and only in England
does the Leblanc process hold its ground.
Health interests have exercised an important bearing on the development
of the industries in question. At first, in the Leblanc process the
hydrochloric acid gas was allowed to escape into the atmosphere, being
regarded as a useless bye-product. Its destructive action on plant
life and the inconvenience caused to the neighbourhood, in spite of
erection of high chimneys, demanded intervention. In England the evils
led to the enactment of the Alkali Acts—the oldest classical legislative
measures bearing on factory hygiene—by which the Leblanc factories were
required to condense the vapour by means of its absorption in water, and
this solution of the acid is now a highly valued product. And, again,
production of nuisance—inconvenience to the neighbourhood through the
soda waste—was the main cause of ousting one of the oldest and most
generally used methods of chemical industrial production. Although every
effort was made to overcome the difficulties, the old classical Leblanc
process is gradually but surely yielding place to the modern Solvay
process, which has no drawback on grounds of health.
We outline next the main features of the _Leblanc soda process_, which
includes, as has been mentioned, also the manufacture of hydrochloric
acid, sodium sulphate and sulphide.
The first part of the process consists in the production of the sulphate
from salt and sulphuric acid, during which hydrochloric acid is formed;
this is carried out in two stages represented in the following formulæ:
1. NaCl + H₂SO₄ = NaHSO₄ + HCl.
2. NaCl + NaHSO₄ = Na₂SO₄ + HCl.
The first stage in which bisulphate is produced is carried out at a
moderate heat, the second requires a red heat. The reactions, therefore,
are made in a furnace combining a pan and muffle furnace.
This saltcake muffle furnace is so arranged that the pan can be shut
off from the muffle by a sliding-door (D). The pan (A) and muffle (E)
have separate flues for carrying off the hydrochloric acid developed (B,
F). First, common salt is treated with sulphuric (Glover) acid in the
cast-iron pan. When generation of hydrochloric acid vapour has ceased,
the sliding-door is raised and the partly decomposed mixture is pushed
through into the muffle, constructed of fire-resisting bricks and tiles,
and surrounded by the fire gases. While the muffle is being raised to
red heat, the sulphate must be repeatedly stirred with a rake in order,
finally, while still hot and giving off acid vapour, to be drawn out at
the working doors into iron boxes provided with doors, where the material
cools. The acid vapour given off when cooling is drawn through the top of
the box into the furnace.
[Illustration: FIG. 3.—Saltcake Muffle Furnace—Section _(after Ost_)
A Pan; B, F Pipes for hydrochloric acid vapour; D Shutter; E Muffle, O
Coke fire.]
Mechanical stirrers, despite their advantage from a health point of view,
have not answered because of their short life.
The valuable bye-product of the sulphate process, _hydrochloric acid_, is
led away separately from the pan and the muffle, as is seen, into one
absorption system. The reason of the separation is that the gas from the
pan is always the more concentrated. The arrangement of the absorbing
apparatus is illustrated in fig. 4.
[Illustration: FIG. 4A.—Preparation of Hydrochloric Acid—Plan (_after
Lueger_)
A, A´ Earthenware pipes
B, B´ Sandstone cooling towers
C, C Series of Woulff’s bottles
D, E Condenser wash towers
FIG. 4B.—Elevation]
The gases are led each through earthenware pipes or channels of stone
pickled with tar (A´), first into small towers of Yorkshire flags (B),
where they are cooled and freed from flue dust and impurities (sulphuric
acid) by washing. They are next led through a series (over fifty) of
Woulff bottles (bombonnes) one metre high, made of acid-resisting
stoneware. The series is laid with a slight inclination towards the
furnace, and water trickles through so that the gases coming from the
wash towers are brought into contact with water in the one case already
almost saturated, whilst the gas which is poorest in hydrochloric acid
meets with fresh water. From the bombonne situated next to the wash tower
the prepared acid is passed as a rule through another series. The last
traces of hydrochloric acid are then removed by leading the gases from
the Woulff bottles up two water towers of stoneware (D and E), which are
filled partly with earthenware trays and partly with coke; above are
tanks from which the water trickles down over the coke. The residual
gases from both sets of absorbing apparatus now unite in a large Woulff
bottle before finally being led away through a duct to the chimney stack.
Less frequently absorption of hydrochloric acid is effected without use
of Woulff bottles, principally in wash towers such as the Lunge-Rohrmann
plate tower.
In the purification of hydrochloric acid, de-arsenicating by sulphuretted
hydrogen or by barium sulphide, &c., and separation of sulphuric acid by
addition of barium chloride, have to be considered.
Another method for production of sulphate and hydrochloric acid, namely,
the Hargreaves process, is referred to later.
We return now to the further working up of the sodium sulphate into
sulphide and soda. The conversion of the sulphate into soda by the
Leblanc method is effected by heating with coal and calcium carbonate,
whereby, through the action of the coal, sodium sulphide forms first,
which next with the calcium carbonate becomes converted into sodium
carbonate and calcium sulphide.
The reactions are:
Na₂SO₄ + 2C = Na₂S + 2CO₂
Na₂S + CaCO₃ = Na₂CO₃ + CaS
CaCO₃ + C = CaO + 2CO.
The reactions are carried out in small works in open reverberatory
furnaces having two platforms on the hearth, and with continuous raking
from one to the other which, as the equations show, cause escape of
carbonic acid gas and carbonic oxide.
Such handworked furnaces, apart from their drawbacks on health grounds,
have only a small capacity, and in large works their place is taken by
revolving furnaces—closed, movable cylindrical furnaces—in which handwork
is replaced by the mechanical revolution of the furnace and from which a
considerably larger output and a product throughout good in quality are
obtained.
The _raw soda_ thus obtained in the black ash furnace is subjected to
lixiviation by water in iron tanks in which the impurities or tank
waste (see below) are deposited. The crude soda liquor so obtained is
then further treated and converted into calcined soda, crystal soda, or
caustic soda. In the production of calcined soda the crude soda liquor is
first purified (‘oxidised’ and ‘carbonised’) by blowing through air and
carbonic acid gas, pressed through a filter press, and crystallised by
evaporation in pans and calcined, i.e. deprived of water by heat.
[Illustration: FIG. 5.—Revolving Black Ash Furnace—Elevation (_after
Lueger_)
A Firing hearth; B Furnace; C Dust box.]
_Crystal soda_ is obtained from well-purified tank liquor by
crystallising in cast-iron vessels.
Caustic soda is obtained by introducing lime suspended in iron cages into
the soda liquor in iron caustic pots, heating with steam, and agitating
by blowing in air.
The resulting clear solution is drawn off and evaporated in cast-iron
pans.
As already mentioned, the _tank waste_ in the Leblanc process, which
remains behind—in amount about equal to the soda produced after
lixiviation of the raw soda with water—constitutes a great nuisance.
It forms mountains round the factories, and as it consists principally
of calcium sulphide and calcium carbonate, it easily weathers under
the influence of air and rain, forming soluble sulphur compounds and
developing sulphuretted hydrogen gas—an intolerable source of annoyance
to the district.
At the same time all the sulphur introduced into the industry as
sulphuric acid is lost in the tank waste. This loss of valuable material
and the nuisance created led to attempts—partially successful—to recover
the sulphur.
The best results are obtained by the Chance-Claus method, in which the
firebrick ‘Claus-kiln’ containing ferric oxide (previously heated to
dull redness) is used. In this process calcium sulphide is acted on by
carbonic acid with evolution of gas so rich in sulphuretted hydrogen that
it can be burnt to sulphur dioxide and used in the lead chambers for
making sulphuric acid. Sulphur also as such is obtained by the method.
These sulphur-recovery processes which have hardly been tried on
the Continent—only the United Alkali Company in England employs the
Chance-Claus on a large scale—were, as has been said, not in a position
to prevent the downfall of the Leblanc soda industry. Before describing
briefly the Solvay method a word is needed as to other processes for
manufacture of sulphate and hydrochloric acid.
_Hargreaves’ process_ produces sodium sulphate (without previous
conversion of sulphur dioxide into sulphuric acid) directly by the
passage of gases from the pyrites burners, air and steam, through salt
blocks placed in vertical cast-iron retorts, a number of which are
connected in series. A fan draws the gases through the system and leads
the hydrochloric acid fumes to the condenser.
Sodium sulphate is used in the manufacture of glass, ultramarine, &c.
Further, the sulphate is converted into Glauber’s salts by dissolving the
anhydrous sulphate obtained in the muffle furnace, purifying with lime,
and allowing the clear salt solution to crystallise out in pans.
A further use of the sulphate is the preparation of sodium sulphide,
which is effected (as in the first part of the Leblanc soda process) by
melting together sulphate and coal in a reverberatory furnace. If the
acid sulphate (bisulphate) or sulphate containing bisulphate is used much
sulphur dioxide gas comes off.
The mass is then lixiviated in the usual soda liquor vats and the lye
either treated so as to obtain crystals or evaporated to strong sodium
sulphide which is poured like caustic soda into metal drums where it
solidifies.
In _Solvay’s ammonia soda process_ ammonia recovered from the waste
produced in the industry is led into a solution of salt until saturation
is complete. This is effected generally in column apparatus such as is
used in distillation of spirit. The solution is then driven automatically
by compressed air to the carbonising apparatus in which the solution
is saturated with carbonic acid; this apparatus is a cylindrical tower
somewhat similar to the series of vessels used for saturating purposes in
sugar factories through which carbonic acid gas passes. In this process
crystalline bi-carbonate of soda is first formed, which is separated
from the ammoniacal mother liquor by filtration, centrifugalisation,
and washing. The carbonate is then obtained by heating (calcining in
pans), during which carbonic acid gas escapes, and this, together with
the carbonic acid produced in the lime kilns, is utilised for further
carbonisation again. The lime formed during the production of carbonic
acid in the lime kilns serves to drive the ammonia out of the ammoniacal
mother liquor, so that the ammonia necessary for the process is recovered
and used over and over again. The waste which results from the action of
the lime on the ammonium chloride liquor is harmless—calcium chloride
liquor.
The _electrolytic_ manufacture of soda from salt requires mention, in
which chlorine (at the anode) and caustic soda (at the cathode) are
formed; the latter is treated with carbonic acid to make soda.
EFFECTS ON HEALTH.—Leymann’s observations show that in the department
concerned with the Leblanc soda process and production of sodium
sulphide, relatively more sickness is noted than, for example, in the
manufacture of sulphuric and nitric acids.
In the preparation of the sulphate, possibility of injury to health or
poisoning arises from the fumes containing hydrochloric or sulphuric acid
in operations at the muffle furnace; in Hargreaves’ process there may be
exposure to the effect of sulphur dioxide. Hydrochloric and sulphuric
acid vapours can escape from the muffle furnace when charging, from
leakages in it, and especially when withdrawing the still hot sulphate.
Large quantities of acid vapours escape from the glowing mass, especially
if coal is not added freely and if it is not strongly calcined. Persons
employed at the saltcake furnaces suffer, according to Jurisch, apart
from injury to the lungs, from defective teeth. The teeth of English
workers especially, it is said, from the practice of holding flannel in
their mouths with the idea of protecting themselves from the effect of
the vapours, are almost entirely eroded by the action of the hydrochloric
acid absorbed by the saliva. Hydrochloric acid vapour, further, can
escape from the absorbing apparatus if this is not kept entirely
sealed, and the hydrochloric acid altogether absorbed—a difficult
matter. Nevertheless, definite acute industrial poisoning from gaseous
hydrochloric acid is rare, no doubt because the workers do not inhale it
in concentrated form.
Injury to the skin from the acid absorbed in water may occur in filling,
unloading, and transport, especially when in carboys, but the burns,
if immediately washed, are very slight in comparison with those from
sulphuric or nitric acids. Injury to health or inconvenience from
sulphuretted hydrogen is at all events possible in the de-arsenicating
process by means of sulphuretted hydrogen gas. At the saltcake furnace
when worked by hand the fumes containing carbonic oxide gas may be
troublesome. In the production of caustic soda severe corrosive action on
the skin is frequent. Leymann found that 13·8 per cent. of the persons
employed in the caustic soda department were reported as suffering from
burns, and calls attention to the fact that on introducing the lime
into the hot soda lye the contents of the vessel may easily froth over.
Heinzerling refers to the not infrequent occurrence of eye injuries in
the preparation of caustic soda, due to the spurting of lye or of solid
particles of caustic soda.
The tank waste gives rise, as already stated, to inconvenience from the
presence of sulphuretted hydrogen. In the recovery of the sulphur and
treatment of the tank waste, sulphuretted hydrogen and sulphur dioxide
gases are evolved. According to Leymann, workers employed in removing
the waste and at the lye vats frequently suffer from inflammation of
the eyes. Further, disturbance of digestion has been noted in persons
treating the tank waste, which Leymann attributes to the unavoidable
development of sulphuretted hydrogen gas.
In the manufacture of sodium sulphide similar conditions prevail. Leymann
found in this branch relatively more cases of sickness than in any other;
diseases of the digestive tract especially appeared to be more numerous.
Leymann makes the suggestion that occurrence of disease of the digestive
organs is either favoured by sodium sulphide when swallowed as dust, or
that here again sulphuretted hydrogen gas plays a part. Further corrosive
effect on the skin and burns may easily arise at work with the hot
corrosive liquor.
In the Solvay ammonia process ammonia and carbonic acid gas are present,
but, so far as I know, neither injury to health nor poisoning have been
described among persons employed in the process. Indeed, the view is
unanimous that this method of manufacture with its technical advantages
has the merit also of being quite harmless. As may be seen from the
preceding description of the process there is no chance of the escape of
the gases named into the workrooms.
USE OF SULPHATE AND SULPHIDE
_Ultramarine_ is made from a mixture of clay, sulphate (Glauber’s
salts), and carbon—sulphate ultramarine; or clay, sulphur, and
soda—soda ultramarine. These materials are crushed, ground, and burnt
in muffle furnaces. On heating the mass in the furnace much sulphur
dioxide escapes, which is a source of detriment to the workmen and the
neighbourhood.
_Sulphonal_ (CH₃)₂C(SO₂C₂H₅)₂, diethylsulphone dimethylmethane,
used medically as a hypnotic, is obtained from mercaptan formed by
distillation of ethyl sulphuric acid with sodium or potassium sulphide.
The mercaptan is converted into mercaptol, and this by oxidation with
potassium permanganate into sulphonal. The volatile mercaptan has a most
disgusting odour, and clings for a long time even to the clothes of those
merely passing through the room.
_Diethyl sulphate_ ((C₂H₅)₂SO₄).—Diethyl sulphate obtained by the
action of sulphuric acid on alcohol has led to poisoning characterised
by corrosive action on the respiratory tract.[1] As the substance in
the presence of water splits up into sulphuric acid and alcohol, this
corrosive action is probably due to the acid. It is possible, however,
that the molecule of diethyl sulphate as such has corrosive action.
Contact with diethyl sulphate is described as having led to fatal
poisoning.[2]
A chemist when conducting a laboratory experiment dropped a glass flask
containing about 40 c.c. of diethyl sulphate, thereby spilling some over
his clothes. He went on working, and noticed burns after some time,
quickly followed by hoarseness and pain in the throat. He died of severe
inflammation of the lungs. A worker in another factory was dropping
diethyl sulphate and stirring it into an at first solid, and later
semi-liquid, mass for the purpose of ethylating a dye stuff. In doing
so he was exposed to fumes, and at the end of the work complained of
hoarseness and smarting of the eyes. He died of double pneumonia two days
later. Post mortem very severe corrosive action on the respiratory tract
was found, showing that the diethyl sulphuric acid had decomposed inside
the body and that nascent sulphuric acid had given rise to the severe
burns. The principal chemist who had superintended the process suffered
severely from hoarseness at night, but no serious consequences followed.
It is stated also that workmen in chemical factories coming into contact
with the fumes of diethyl sulphate ester suffer from eye affections.[3]
CHLORINE, CHLORIDE OF CALCIUM, AND CHLORATES
MANUFACTURE.—The older processes depend on the preparation of chlorine
and hydrochloric acid by an oxidation process in which the oxidising
agent is either a compound rich in oxygen—usually common manganese
dioxide (pyrolusite)—or the oxygen of the air in the presence of heated
copper chloride (as catalytic agent). The former (Weldon process) is
less used now than either the latter (Deacon process) or the electrolytic
manufacture of chlorine.
In the _Weldon process_ from the still liquors containing manganous
chloride the manganese peroxide is regenerated, and this so regenerated
Weldon mud, when mixed with fresh manganese dioxide, is used to initiate
the process. This is carried out according to the equations:
MnO₂ + 4HCl = MnCl₄ + 2H₂O
MnCl₄ = MnCl₂ + Cl₂.
[Illustration: FIG. 6.—Preparation of Chlorine—Diaphragm Method (_after
Ost_)]
Hydrochloric acid is first introduced into the chlorine still (vessels
about 3 m. in height, of Yorkshire flag or fireclay), next the Weldon
mud gradually, and finally steam to bring the whole to boiling; chlorine
comes off in a uniform stream. The manganous chloride still liquor is run
into settling tanks. The regeneration of the manganous chloride liquor
takes place in an oxidiser which consists of a vertical iron cylinder in
which air is blown into the heated mixture of manganous chloride and milk
of lime. The dark precipitate so formed, ‘Weldon mud,’ as described, is
used over again, while the calcium chloride liquor runs away.
The _Deacon process_ depends mainly on leading the stream of hydrochloric
acid gas evolved from a saltcake pot mixed with air and heated into a
tower containing broken bricks of the size of a nut saturated with
copper chloride. Chlorine is evolved according to the equation:
2HCl + O = 2Cl + H₂O.
[Illustration: FIG. 7.—Preparation of Chlorine—Bell Method (_after Ost_)]
The _electrolytic production_ of chlorine with simultaneous production
of _caustic alkali_ is increasing and depends on the splitting up of
alkaline chlorides by a current of electricity. The chlorine evolved at
the anode and the alkaline liquor formed at the cathode must be kept
apart to prevent secondary formation of hypochlorite and chlorate (see
below). This separation is generally effected in one of three ways: (1)
In the diaphragm process (Griesheim-Elektron chemical works) the anode
and cathode are kept separate by porous earthenware diaphragms arranged
as illustrated in fig. 6. The anode consists of gas carbon, or is made
by pressing and firing a mixture of charcoal and tar; it lies inside the
diaphragm. The chlorine developed in the anodal cell is carried away by
a pipe. The metal vessel serves as the cathode. The alkali, which, since
it contains chloride, is recovered as caustic soda after evaporation
and crystallisation, collects in the cathodal space lying outside the
diaphragm. (2) By the Bell method (chemical factory at Aussig) the
anodal and cathodal fluids, which keep apart by their different specific
weights, are separated by a stoneware bell; the poles consist of sheet
iron and carbon. The containing vessel is of stoneware. (3) In the
mercury process (England) sodium chloride is electrolysed without a
diaphragm, mercury serving as the cathode. This takes up the sodium,
which is afterwards recovered from the amalgam formed by means of water.
If _chlorate_ or _hypochlorite_ is to be obtained electrolytically,
electrodes of the very resistant but expensive platinum iridium are used
without a diaphragm. Chlorine is developed—not free, but combined with
the caustic potash. The bleaching fluid obtained electrolytically in this
way is a rival of bleaching powder.
_Bleaching powder_ is made from chlorine obtained by the Weldon or Deacon
process. Its preparation depends on the fact that calcium hydrate takes
up chlorine in the cold with formation of calcium hypochlorite after the
equation:
2Ca(OH)₂ + 4Cl = Ca(ClO)₂ + CaCl₂ + 2H₂O.
The resulting product contains from 35 to 36 per cent. chlorine, which is
given off again when treated with acids.
The preparation of chloride of lime takes place in bleaching powder
chambers made of sheets of lead and Yorkshire flagstones. The lime is
spread out on the floors of these and chlorine introduced. Before the
process is complete the lime must be turned occasionally.
In the manufacture of bleaching powder from Deacon chlorine, Hasenclever
has constructed a special cylindrical apparatus (fig. 8), consisting of
several superimposed cast-iron cylinders in which are worm arrangements
carrying the lime along, while chlorine gas passes over in an opposite
direction. This continuous process is, however, only possible for the
Deacon chlorine strongly diluted with nitrogen and oxygen and not for
undiluted Weldon gas.
_Liquid chlorine_ can be obtained by pressure and cooling from
concentrated almost pure Weldon chlorine gas.
_Potassium chlorate_, which, as has been said, is now mostly obtained
electrolytically, was formerly obtained by passing Deacon chlorine into
milk of lime and decomposing the calcium chlorate formed by potassium
chloride.
Chlorine and chloride of lime are used for bleaching; chlorine further
is used in the manufacture of colours; chloride of lime as a mordant in
cloth printing and in the preparation of chloroform; the chlorates are
oxidising agents and used in making safety matches. The manufacture of
organic chlorine products will be dealt with later.
[Illustration: FIG. 8.—Preparation of Bleaching Powder. Apparatus of
Hasenclever (_after Ost_)
A Hopper for slaked lime; W Worm conveying lime; Z Toothed wheels;
K Movable covers; C Entrance for chlorine gas; D Pipe for escape of
chlorine-free gas; B Outlet shoot for bleaching powder]
EFFECTS ON HEALTH.—In these industries the possibility of injury to
health and poisoning by inhalation of chlorine gas is prominent. Leymann
has shown that persons employed in the manufacture of chlorine and
bleaching powder suffer from diseases of the respiratory organs 17·8 per
cent., as contrasted with 8·8 per cent. in other workers: and this is
without doubt attributable to the injurious effect of chlorine gas, which
it is hardly possible to avoid despite the fact that Leymann’s figures
refer to a model factory. But the figures show also that as the industry
became perfected the number of cases of sickness steadily diminished.
Most cases occur from unsatisfactory conditions in the production of
chloride of lime, especially if the chloride of lime chambers leak, if
the lime is turned over while the chlorine is being let in, by too early
entrance into chambers insufficiently ventilated, and by careless and
unsuitable methods of emptying the finished bleaching powder.
The possibility of injury is naturally greater from the concentrated gas
prepared by the Weldon process than from the diluted gas of the Deacon
process—the more so as in the latter the bleaching powder is made in
the Hasenclever closed-in cylindrical apparatus in which the chlorine
is completely taken up by the lime. The safest process of all is the
electrolytic, as, if properly arranged, there should be no escape of
chlorine gas. The chlorine developed in the cells (when carried out on
the large scale) is drawn away by fans and conducted in closed pipes to
the place where it is used.
Many researches have been published as to the character of the skin
affection well known under the name of _chlorine rash_ (chlorakne).
Some maintain that it is not due to chlorine at all, but is an eczema
set up by tar. Others maintain that it is due to a combined action of
chlorine and tar. Support to this view is given by the observation that
cases of chlorine rash, formerly of constant occurrence in a factory
for electrolytic manufacture of chlorine, disappeared entirely on
substitution of magnetite at the anode for carbon.[1] The conclusion
seems justified that the constituents of the carbon or of the surrounding
material set up the condition.
Chlorine rash has been observed in an alkali works where chlorine was
not produced electrolytically, and under conditions which suggested that
compounds of tar and chlorine were the cause. In this factory for the
production of salt cake by the Hargreaves’ process cakes of rock salt
were prepared and, for the purpose of drying, conveyed on an endless
metal band through a stove. To prevent formation of crusts the band
was tarred. The salt blocks are decomposed in the usual way by sulphur
dioxide, steam, and oxygen of the air, and the hydrochloric acid vapour
led through Deacon towers in which the decomposition of the hydrochloric
acid into chlorine and water is effected by metal salts in the manner
characteristic of the Deacon process. These salts are introduced in small
earthenware trays which periodically have to be removed and renewed;
the persons engaged in doing this were those affected. The explanation
was probably that the tar sticking to the salt blocks distilled in the
saltcake furnaces and formed a compound with the chlorine which condensed
on the earthenware trays. When contact with these trays was recognised as
the cause, the danger was met by observance of the greatest cleanliness
in opening and emptying the Deacon towers.
Leymann[2] is certain that the rash is due to chlorinated products which
emanate from the tar used in the construction of the cells. And the
affection has been found to be much more prevalent when the contents of
the cells are emptied while the contents are still hot than when they are
first allowed to get cold.
Lehmann[3] has approached the subject on the experimental side, and is of
opinion that probably chlorinated tar derivatives (chlorinated phenols)
are the cause of the trouble. Both he and Roth think that the affection
is due not to external irritation of the skin, but to absorption of the
poisonous substances into the system and their elimination by way of the
glands of the skin.
In the section on manganese poisoning detailed reference is made to the
form of illness recently described in persons employed in drying the
regenerated Weldon mud.
Mercurial poisoning is possible when mercury is used in the production of
chlorine electrolytically.
In the manufacture of chlorates and hypochlorite, bleaching fluids, &c.,
injury to health from chlorine is possible in the same way as has been
described above.
OTHER CHLORINE COMPOUNDS. BROMINE, IODINE, AND FLUORINE
Chlorine is used for the production of a number of organic chlorine
compounds, and in the manufacture of bromine and iodine, processes
which give rise to the possibility of injury to health and poisoning by
chlorine; further, several of the substances so prepared are themselves
corrosive or irritating or otherwise poisonous. Nevertheless, severe
poisoning and injurious effects can be almost entirely avoided by
adoption of suitable precautions. In the factory to which Leymann’s
figures refer, where daily several thousand kilos of chlorine and organic
chlorine compounds are prepared, a relatively very favourable state of
health of the persons employed was noted. At all events the preparation
of chlorine by the electrolytic process takes place in closed vessels
admirably adapted to avoid any escape of chlorine gas except as the
result of breakage of the apparatus or pipes. When this happens, however,
the pipes conducting the gas can be immediately disconnected and the
chlorine led into other apparatus or into the bleaching powder factory.
As such complete precautionary arrangements are not everywhere to be
found, we describe briefly the most important of the industries in
question and the poisoning recognised in them.
_Chlorides of phosphorus._—By the action of dry chlorine on an excess
of heated amorphous phosphorus, trichloride is formed (PCl₃), a
liquid having a sharp smell and causing lachrymation, which fumes
in the air, and in presence of water decomposes into phosphorous
acid and hydrochloric acid. On heating with dry oxidising substances
it forms phosphorus oxychloride (see below), which is used for the
production of acid chlorides. By continuous treatment with chlorine
it becomes converted into phosphorus pentachloride (PCl₅), which also
is conveniently prepared by passing chlorine through a solution of
phosphorus in carbon bisulphide, the solution being kept cold; it is
crystalline, smells strongly, and attacks the eyes and lungs. With excess
of water it decomposes into phosphoric acid and hydrochloric acid:
with slight addition of water it forms phosphorus oxychloride (POCl₃).
On the large scale this is prepared by reduction of phosphate of lime
in the presence of chlorine with carbon or carbonic oxide. Phosphorus
oxychloride, a colourless liquid, fumes in the air and is decomposed by
water into phosphoric acid and hydrochloric acid.
In the preparation of chlorides of phosphorus, apart from the danger of
chlorine gas and hydrochloric acid, the poisonous effect of phosphorus
and its compounds (see Phosphorus) and even of carbon disulphide (as
the solvent of phosphorus) and of carbonic oxide (in the preparation of
phosphorus oxychloride) have to be taken into account.
Further, the halogen compounds of phosphorus exert irritant action on
the eyes and lungs similar to chloride of sulphur as a result of their
splitting up on the moist mucous membranes into hydrochloric acid and an
oxyacid of phosphorus.[4]
Unless, therefore, special measures are taken, the persons employed
in the manufacture of phosphorus chlorides suffer markedly from the
injurious emanations given off.[5]
Leymann[6] mentions one case of poisoning by phosphorus chloride as
having occurred in the factory described by him. By a defect in the
outlet arrangement phosphorus oxychloride flowed into a workroom.
Symptoms of poisoning (sensation of suffocation, difficulty of breathing,
lachrymation, &c.) at once attacked the occupants; before much gas had
escaped, the workers rushed out. Nevertheless, they suffered from severe
illness of the respiratory organs (bronchial catarrh and inflammation of
the lungs, with frothy, blood-stained expectoration, &c.).[7]
_Chlorides of sulphur._—Monochloride of sulphur (S₂Cl₂) is made by
passing dried, washed chlorine gas into molten heated sulphur. The oily,
brown, fuming liquid thus made is distilled over into a cooled condenser
and by redistillation purified from the sulphur carried over with it.
Sulphur monochloride can take up much sulphur, and when saturated is used
in the vulcanisation of indiarubber, and, further, is used to convert
linseed and beetroot oil into a rubber substitute. Monochloride of
sulphur is decomposed by water into sulphur dioxide, hydrochloric acid,
and sulphur. By further action of chlorine on the monochloride, sulphur
dichloride (SCl₂) and the tetrachloride (SCl₄) are formed.
In its preparation and use (see also Indiarubber Manufacture) the
injurious action of chlorine, of hydrochloric acid, and of sulphur
dioxide comes into play.
The monochloride has very irritating effects. Leymann cites an industrial
case of poisoning by it. In the German factory inspectors’ reports for
1897 a fatal case is recorded. The shirt of a worker became saturated
with the material owing to the bursting of a bottle. First aid was
rendered by pouring water over him, thereby increasing the symptoms,
which proved fatal the next day. Thus the decomposition brought about by
water already referred to aggravated the symptoms.
_Zinc chloride_ (ZnCl₂) is formed by heating zinc in presence of
chlorine. It is obtained pure by dissolving pure zinc in hydrochloric
acid and treating this solution with chlorine. Zinc chloride is
obtained on the large scale by dissolving furnace calamine (zinc
oxide) in hydrochloric acid. Zinc chloride is corrosive. It is used
for impregnating wood and in weighting goods. Besides possible injury
to health from chlorine and hydrogen chloride, risk of arseniuretted
hydrogen poisoning is present in the manufacture if the raw materials
contain arsenic. Eulenburg considers that in soldering oppressive zinc
chloride fumes may come off if the metal to be soldered is first wiped
with hydrochloric acid and then treated with the soldering iron.
_Rock salt._—Mention may be made that even to salt in combination with
other chlorides (calcium chloride, magnesium chloride, &c.) injurious
effects are ascribed. Ulcers and perforation of the septum of the nose in
salt-grinders and packers who were working in a room charged with salt
dust are described.[8] These effects are similar to those produced by the
bichromates.
Organic Chlorine Compounds
_Carbon oxychloride_ (COCl₂, carbonyl dichloride, phosgene) is produced
by direct combination of chlorine and carbonic oxide in presence of
animal charcoal. Phosgene is itself a very poisonous gas which, in
addition to the poisonous qualities of carbonic oxide (which have to be
borne in mind in view of the method of manufacture), acts as an irritant
of the mucous membranes. Commercially it is in solution in toluene and
xylene, from which the gas is readily driven off by heating. It is used
in the production of various colours, such as crystal violet, Victoria
blue, auramine, &c.
A fatal case of phosgene gas poisoning in the report of the Union of
Chemical Industry for 1905 deserves mention. The phosgene was kept in a
liquefied state in iron bottles provided with a valve under 2·3 atm.
pressure. The valve of one of these bottles leaked, allowing large escape
into the workroom. Two workers tried but failed to secure the valve. The
cylinder was therefore removed by a worker, by order of the manager,
and placed in a cooling mixture, as phosgene boils at 8° C. The man in
question wore a helmet into which air was pumped from the compressed air
supply in the factory. As the helmet became obscured through moisture
after five minutes the worker took it off. A foreman next put on the
cleaned mask, and kept the cylinder surrounded with ice and salt for
three-quarters of an hour, thus stopping the escape of gas. Meanwhile,
the first worker had again entered the room, wearing a cloth soaked in
dilute alcohol before his mouth, in order to take a sack of salt to the
foreman. An hour and a half later he complained of being very ill, became
worse during the night, and died the following morning. Although the
deceased may have been extremely susceptible, the case affords sufficient
proof of the dangerous nature of the gas, which in presence of moisture
had decomposed into carbonic acid and hydrochloric acid; the latter had
acutely attacked the mucous membrane of the respiratory passages and set
up fatal bronchitis. Further, it was found that the leaden plugs of the
valves had been eroded by the phosgene.
Three further cases of industrial phosgene poisoning have been
reported,[9] one a severe case in which there was bronchitis with
blood-stained expectoration, great dyspnœa, and weakness of the heart’s
action. The affected person was successfully treated with ether and
oxygen inhalations. Phosgene may act either as the whole molecule, or is
inhaled to such degree that the carbonic oxide element plays a part.
In another case of industrial phosgene poisoning the symptoms were those
of severe irritation of the bronchial mucous membrane and difficulty of
breathing.[10] The case recovered, although sensitiveness of the air
passages lasted a long time.
_Carbon chlorine compounds_ (_aliphatic series_).—_Methyl chloride_
(CH₃Cl) or chlormethane is prepared from methyl alcohol and hydrochloric
acid (with chloride of zinc) or methyl alcohol, salt, and sulphuric acid.
It is prepared in France on a large scale from beetroot _vinasse_ by dry
distillation of the evaporation residue. The distillate, which contains
methyl alcohol, trimethylamine, and other methylated amines, is heated
with hydrochloric acid; the methyl chloride so obtained is purified,
dried and compressed. It is used in the preparation of pure chloroform,
in the coal-tar dye industry, and in surgery (as a local anæsthetic). In
the preparation of methyl chloride there is risk from methyl alcohol,
trimethylamine, &c. Methyl chloride itself is injurious to health.
_Methylene chloride_ (CH₂Cl₂, dichlormethane) is prepared in a similar
way. It is very poisonous.
_Carbon tetrachloride_ (CCl₄, tetrachlormethane) is technically
important. It is prepared by passing chlorine gas into carbon bisulphide
with antimony or aluminium chloride. Carbon tetrachloride is a liquid
suitable for the extraction of fat or grease (as in chemical cleaning),
and has the advantage of being non-inflammable. Carbon tetrachloride, so
far as its poisonous qualities are concerned, is to be preferred to other
extractives (see Carbon Bisulphide, Benzine, &c.); for the rest it causes
unconsciousness similar to chloroform.
When manufactured industrially, in addition to the poisonous effect of
chlorine, the poisonous carbon bisulphide has also to be borne in mind.
_Ethyl chloride_ (C₂H₅Cl) is made in a way analogous to methyl chloride
by the action of hydrochloric acid on ethyl alcohol and chloride of zinc.
It is used in medicine as a narcotic.
_Monochloracetic acid._—In the preparation of monochloracetic acid
hydrochloric acid is developed in large quantity. From it and anthranilic
acid artificial indigo is prepared (according to Heuman) by means of
caustic potash.
_Chloral_ (CCl₃CHO, trichloracetaldehyde) is produced by chlorinating
alcohol. Chloral is used in the preparation of pure chloroform and (by
addition of water) of chloral hydrate (trichloracetaldehyde hydrate), the
well-known soporific.
_Chloroform_ (CHCl₃, trichlormethane).—Some methods for the preparation
of chloroform have been already mentioned (Chloral, Methyl Chloride).
Technically it is prepared by distillation of alcohol or acetone with
bleaching powder. The workers employed are said to be affected by the
stupefying vapours. Further, there is the risk of chlorine gas from use
of chloride of lime.
_Chloride of nitrogen_ (NCl₃) is an oily, volatile, very explosive,
strongly smelling substance, which irritates the eyes and nose violently
and is in every respect dangerous; it is obtained from the action of
chlorine or hypochlorous acid on sal-ammoniac. The poisonous nature of
these substances may come into play. Risk of formation of chloride of
nitrogen can arise in the production of gunpowder from nitre containing
chlorine.
_Cyanogen chloride_ (CNCl).—Cyanogen chloride is made from hydrocyanic
acid or cyanide of mercury and chlorine. Cyanogen chloride itself is an
extremely poisonous and irritating gas, and all the substances from which
it is made are also poisonous. According to Albrecht cyanogen chloride
can arise in the preparation of red prussiate of potash (by passage of
chlorine gas into a solution of the yellow prussiate) if the solution is
treated with chlorine in excess; the workers may thus be exposed to great
danger.
_Chlorobenzene._—In his paper referred to Leymann cites three cases of
poisoning by chlorobenzene, one by dinitrochlorobenzene, and, further,
three cases of burning by chlorobenzene and one by benzoyl chloride
(C₆H₅COCl). The last named is made by treating benzaldehyde with
chlorine, and irritates severely the mucous membranes, while decomposing
into hydrochloric acid and benzoic acid.[11] Benzal chloride (C₆H₅CHCl₂),
benzo trichloride (C₆H₅CCl₃), and benzyl chloride (C₆H₅CH₂Cl) are
obtained by action of chlorine on boiling toluene. The vapours of these
volatile products irritate the respiratory passages. In the manufacture
there is risk from the effect of chlorine gas and toluene vapour (see
Benzene, Toluene).
Leymann[12] describes in detail six cases of poisoning in persons
employed in a chlorobenzene industry, of which two were due to
nitrochlorobenzene. Symptoms of poisoning—headache, cyanosis, fainting,
&c.—were noted in a person working for three weeks with chlorobenzene.[13]
In Lehmann’s opinion chlorine rash, the well-recognised skin affection
of chlorine workers, may be due to contact with substances of the
chlorbenzol group.[14]
_Iodine and iodine compounds._—Formerly iodine was obtained almost
exclusively from the liquor formed by lixiviation of the ash of seaweed
(kelp, &c.); now the principal sources are the mother liquors from
Chili saltpetre and other salt industries. From the concentrated liquor
the iodine is set free by means of chlorine or oxidising substances
and purified by distillation and sublimation. Iodine is used for the
preparation of photographic and pharmaceutical preparations, especially
iodoform (tri-iodomethane, CHI₃), which is made by acting with iodine and
caustic potash on alcohol, aldehyde, acetone, &c.
Apart from possible injurious action of chlorine when used in the
preparation of iodine, workers are exposed to the possibility of chronic
iodine poisoning. According to Ascher[15] irritation effects, nervous
symptoms, and gastric ulceration occur in iodine manufacture and use.
He considers that bromide of iodine used in photography produces these
irritating effects most markedly. Layet and also Chevallier in older
literature have made the same observations.
The Swiss Factory Inspectors’ Report for 1890-1 describes two acute
cases of iodine poisoning in a factory where organic iodine compounds
were made; one terminated fatally (severe cerebral symptoms, giddiness,
diplopia, and collapse).
_Bromine and bromine compounds._—Bromine is obtained (as in the case of
iodine) principally from the mother liquors of salt works (especially
Stassfurt saline deposits) by the action of chlorine or nascent oxygen
on the bromides of the alkalis and alkaline earths in the liquors. They
are chiefly used in photography (silver bromide), in medicine (potassium
bromide, &c.), and in the coal-tar dye industry.
The danger of bromine poisoning (especially of the chronic form) is
present in its manufacture and use, but there is no positive evidence of
the appearance of the bromine rash among the workers. On the other hand,
instances are recorded of poisoning by methyl bromide, and the injurious
effect of bromide of iodine has been referred to.
_Methyl iodide and methyl bromide._—Methyl iodide (CH₃I), a volatile
fluid, is obtained by distillation of wood spirit with amorphous
phosphorus and iodine; it is used in the production of methylated
tar colours and for the production of various methylene compounds.
Grandhomme describes, in the paper already referred to, six cases, some
very severe, of poisoning by the vapour of methyl iodide among workers
engaged in the preparation of antipyrin, which is obtained by the action
of aceto-acetic ether on phenyl hydrazine, treatment of the pyrazolone
so obtained with methyl iodide, and decomposition of the product with
caustic soda. A case of methyl iodide poisoning is described in a factory
operative, who showed symptoms similar to those described for methyl
bromide except that the psychical disturbance was more marked.[16]
Three cases of methyl bromide (CH₃Br) poisoning are described in persons
preparing the compound.[17] One of these terminated fatally. There
is some doubt as to whether these cases were really methyl bromide
poisoning. But later cases of methyl bromide poisoning are known, and
hence the dangerous nature of this chemical compound is undoubted. Thus
the Report of the Union of Chemical Industry for 1904 gives the following
instance: Two workers who had to deal with an ethereal solution of methyl
bromide became ill with symptoms of alcoholic intoxication. One suffered
for a long time from nervous excitability, attacks of giddiness, and
drowsiness. Other cases of poisoning from methyl bromide vapour are
recorded with severe nervous symptoms and even collapse.
_Fluorine compounds._—_Hydrogen fluoride_ (HFl) commercially is a watery
solution, which is prepared by decomposition of powdered fluorspar by
sulphuric acid in cast-iron vessels with lead hoods. The escaping fumes
are collected in leaden condensers surrounded with water; sometimes to
get a very pure product it is redistilled in platinum vessels.
Hydrogen fluoride is used in the preparation of the fluorides of
antimony, of which antimony fluoride ammonium sulphate (SbFl₃(NH₄)₂SO₄)
has wide use in dyeing as a substitute for tartar emetic. It is produced
by dissolving oxide of antimony in hydrofluoric acid with addition of
ammonium sulphate and subsequent concentration and crystallisation.
Hydrofluoric acid is used for etching glass (see also Glass Industry).
In brewing, an unpurified silico-fluoric acid mixed with silicic acid,
clay, oxide of iron, and oxide of zinc called Salufer is used as a
disinfectant and preservative.
_Hydrofluoric acid and silicofluoric acid_ (H₂SiFl₆) arise further
in the superphosphate industry by the action of sulphuric acid on the
phosphorites whereby silicofluoric acid is obtained as a bye-product
(see also Manufacture of Artificial Manure). Hydrofluoric acid and its
derivatives both in their manufacture and use and in the superphosphate
industry affect the health of the workers.
If hydrogen fluoride or its compounds escape into the atmosphere they
attack the respiratory passages and set up inflammation of the eyes;
further, workers handling the watery solutions are prone to skin
affections (ulceration).
The following are examples of the effects produced.[18] A worker in an
art establishment upset a bottle of hydrofluoric acid and wetted the
inner side of a finger of the right hand. Although he immediately washed
his hands, a painful inflammation with formation of blisters similar to a
burn of the second degree came on within a few hours. The blister became
infected and suppurated.
A man and his wife wished to obliterate the printing on the top of
porcelain beer bottle stoppers with hydrofluoric acid. The man took a
cloth, moistened a corner of it, and then rubbed the writing off. After a
short time he noticed a slight burning sensation and stopped. His wife,
who wore an old kid glove in doing the work, suffered from the same
symptoms, the pain from which in the night became unbearable, and in
spite of medical treatment gangrene of the finger-tips ensued. Healing
took place with suppuration and loss of the finger-nails.
Injury of the respiratory passages by hydrofluoric acid has often been
reported. In one factory for its manufacture the hydrofluoric acid vapour
was so great that all the windows to a height of 8 metres were etched
dull.
Several cases of poisoning by hydrofluoric acid were noted by me when
examining the certificates of the Sick Insurance Society of Bohemia. In
1906 there were four due to inhalation of vapour of hydrofluoric acid in
a hydrofluoric acid factory, with symptoms of corrosive action on the
mucous membrane of the respiratory tract. In 1907 there was a severe case
in the etching of glass.[19]
NITRIC ACID.
MANUFACTURE AND USES.—_Nitric acid_ (HNO₃) is obtained by distillation
when Chili saltpetre (sodium nitrate) is decomposed by sulphuric acid in
cast-iron retorts according to the equation:
NaNO₃ + H₂SO₄ = NaHSO₄ + HNO₃.
Condensation takes place in fireclay Woulff bottles connected to a
coke tower in the same way as has been described in the manufacture of
hydrochloric acid.
[Illustration: FIG. 9.—Preparation of Nitric Acid (_after Ost_)]
Lunge-Rohrmann plate towers are also used instead of the coke tower.
Earthenware fans—as is the case with acid gases generally—serve to
aspirate the nitrous fumes.
To free the nitric acid of the accompanying lower oxides of nitrogen
(as well as chlorine, compounds of chlorine and other impurities) air
is blown into the hot acid. The mixture of sodium sulphate and sodium
bisulphate remaining in the retorts is either converted into sulphate by
addition of salt or used in the manufacture of glass.
The nitric acid obtained is used either as such or mixed with sulphuric
acid or with hydrochloric acid.
Pure nitric acid cannot at ordinary atmospheric pressure be distilled
unaltered, becomes coloured on distillation, and turns red when exposed
to light. It is extremely dangerous to handle, as it sets light to straw,
for example, if long in contact with it. It must be packed, therefore, in
kieselguhr earth, and when in glass carboys forwarded only in trains for
transport of inflammable material.
Red, _fuming nitric acid_, a crude nitric acid, contains much nitrous
and nitric oxides. It is produced if in the distillation process less
sulphuric acid and a higher temperature are employed or (by reduction) if
starch meal is added.
The successful production of nitric acid from the air must be referred
to. It is effected by electric discharges in special furnaces from which
the air charged with nitrous gas is led into towers where the nitric
oxide is further oxidised (to tetroxide), and finally, by contact with
water, converted into nitric acid.
Nitric acid is used in the manufacture of phosphoric acid, arsenious
acid, and sulphuric acid, nitro-glycerin and nitrocellulose, smokeless
powder, &c. (see the section on Explosives), in the preparation of
nitrobenzenes, picric acid, and other nitro-compounds (see Tar Products,
&c.). The diluted acid serves for the solution and etching of metals,
also for the preparation of nitrates, such as the nitrates of mercury,
silver, &c.
EFFECTS ON HEALTH.—Leymann considers that the average number of cases and
duration of sickness among persons employed in the nitric acid industry
are generally on the increase; the increase relates almost entirely to
burns which can hardly be avoided with so strongly corrosive an acid. The
number of burns amounts almost to 12 per cent. according to Leymann’s
figures (i.e. on an average 12 burns per 100 workers), while among the
packers, day labourers, &c., in the same industry the proportion is only
1 per cent. Affections of the respiratory tract are fairly frequent (11·8
per cent. as compared with 8·8 per cent. of other workers), which is no
doubt to be ascribed to the corrosive action of nitrous fumes on the
mucous membranes. Escape of acid fumes can occur in the manufacture of
nitric acid though leaky retorts, pipes, &c., and injurious acid fumes
may be developed in the workrooms from the bisulphate when withdrawn from
the retorts, which is especially the case when excess of sulphuric acid
is used. The poisonous nature of these fumes is very great, as is shown
by cases in which severe poisoning has been reported from merely carrying
a vessel containing fuming nitric acid.[1]
Frequent accidents occur through the corrosive action of the acid or
from breathing the acid fumes—apart from the dangers mentioned in the
manufacture—in filling, packing, and despatching the acid—especially
if appropriate vessels are not used and they break. Of such accidents
several are reported.
Further, reports of severe poisoning from the use of nitric acid are
numerous. Inhalation of nitrous fumes (nitrous and nitric oxides, &c.)
does not immediately cause severe symptoms or death; severe symptoms tend
to come on some hours later, as the examples cited below show.
Occurrence of such poisoning has already been referred to when describing
the sulphuric acid industry. In the superphosphate industry also
poisoning has occurred by accidental development of nitric oxide fumes on
sodium nitrate mixing with very acid superphosphate.
Not unfrequently poisoning arises in pickling metals (belt making,
pickling brass; cf. the chapter on Treatment of Metals). Poisoning by
nitrous fumes has frequently been reported from the action of nitric acid
on organic substances whereby the lower oxides of nitrogen—nitrous and
nitric oxides—are given off. Such action of nitric acid or of a mixture
of nitric and sulphuric acid on organic substances is used for nitrating
purposes (see Nitroglycerin; Explosives; Nitrobenzol).
Through want of care, therefore, poisoning can arise in these industries.
Again, this danger is present on accidental contact of escaping acid with
organic substances (wood, paper, leather, &c.), as shown especially by
fires thus created.[2]
Thus, in a cellar were five large iron vessels containing a mixture of
sulphuric and nitric acids. One of the vessels was found one morning to
be leaking. The manager directed that smoke helmets should be fetched,
intending to pump out the acid, and two plumbers went into the cellar
to fix the pump, staying there about twenty-five minutes. They used
cotton waste and handkerchiefs as respirators, but did not put on the
smoke helmets. One plumber suffered only from cough, but the other died
the same evening with symptoms of great dyspnœa. At the autopsy severe
inflammation and swelling of the mucous membrane of the palate, pharynx
and air passages, and congestion of the lungs were found.
Two further fatal cases in the nitrating room are described by Holtzmann.
One of the two complained only a few hours after entering the room of
pains in the chest and giddiness. He died two days later. The other died
the day after entering the factory, where he had only worked for three
hours. In both cases intense swelling and inflammation of the mucous
membrane was found.
Holtzmann mentions cases of poisoning by nitrous fumes in the heating of
an artificial manure consisting of a mixture of saltpetre, brown coal
containing sulphur, and wool waste. Fatalities have been reported in
workers who had tried to mop up the spilt nitric acid with shavings.[3]
We quote the following other instances[4]:
(1) Fatal poisoning of a fireman who had rescued several persons from a
room filled with nitrous fumes the result of a fire occasioned by the
upsetting of a carboy. The rescued suffered from bronchial catarrh, the
rescuer dying from inflammation and congestion of the lungs twenty-nine
hours after the inhalation of the gas.
(2) At a fire in a chemical factory three officers and fifty-seven
firemen became affected from inhalation of nitrous fumes, of whom one
died.
(3) In Elberfeld on an open piece of ground fifty carboys were stored.
One burst and started a fire. As a strong wind was blowing the firemen
were little affected by the volumes of reddish fumes. Soon afterwards at
the same spot some fifty to sixty carboys were destroyed. Fifteen men
successfully extinguished the fire in a relatively still atmosphere in
less than half an hour. At first hardly any symptoms of discomfort were
felt. Three hours later all were seized with violent suffocative attacks,
which in one case proved fatal and in the rest entailed nine to ten days’
illness from affection of the respiratory organs.
The Report of the Union for Chemical Industry for 1908 describes a
similar accident in a nitro-cellulose factory.
Of those engaged in extinguishing the fire twenty-two were affected, and
in spite of medical treatment and use of the oxygen apparatus three died.
From the same source we quote the following examples:
In a denitrating installation (see Nitro-glycerin; Explosives) a man was
engaged in blowing, by means of compressed air, weak nitric acid from a
stoneware vessel sunk in the ground into a washing tower. As the whole
system was already under high pressure the vessel suddenly exploded, and
in doing so smashed a wooden vat containing similar acid, which spilt on
the ground with sudden development of tetroxide vapours. The man inhaled
much gas, but except for pains in the chest felt no serious symptoms at
the time and continued to work the following day. Death occurred the next
evening from severe dyspnœa.
A somewhat similar case occurred in the nitrating room of a dynamite
factory in connection with the cleaning of a waste acid egg; the vessel
had for several days been repeatedly washed out with water made alkaline
with unslaked lime. Two men then in turn got into the egg in order to
remove the lime and lead deposit, compressed air being continuously blown
in through the manhole. The foreman remained about a quarter of an hour
and finished the cleaning without feeling unwell. Difficulty of breathing
came on in the evening, and death ensued on the following day.
In another case a worker was engaged in washing nitroxylene when, through
a leak, a portion of the contents collected in a pit below. He then
climbed into the pit and scooped the nitroxylene which had escaped into
jars. This work took about three-quarters of an hour, and afterwards he
complained of difficulty of breathing and died thirty-six hours later.[5]
A worker again had to control a valve regulating the flow to two large
vessels serving to heat or cool the nitrated liquid. Both vessels were
provided with pressure gauges and open at the top. Through carelessness
one of the vessels ran over, and instead of leaving the room after
closing the valve, the man tried to get rid of the traces of his error,
remaining in the atmosphere charged with the fumes,[6] and was poisoned.
Nitric and Nitrous Salts and Compounds
When dissolving in nitric acid the substances necessary for making the
various nitrates, nitric and nitrous oxides escape. In certain cases
nitric and hydrochloric acids are used together to dissolve metals such
as platinum and gold and ferric oxides, when chlorine as well as nitrous
oxide escapes. Mention is necessary of the following:
_Barium nitrate_ (Ba(NO₃)₂) is prepared as a colourless crystalline
substance by acting on barium carbonate or barium sulphide with nitric
acid. Use is made of it in fireworks (green fire) and explosives. In
analogous way strontium nitrate (Sr(NO₃)₂) is made and used for red fire.
_Ammonium nitrate_ (NH₄NO₃), a colourless crystalline substance, is
obtained by neutralising nitric acid with ammonia or ammonium carbonate,
and is also made by dissolving iron or tin in nitric acid. It is used in
the manufacture of explosives.
_Lead nitrate_ (Pb(NO₃)₂), a colourless crystalline substance, is made by
dissolving lead oxide or carbonate in nitric acid. It is used in dyeing
and calico printing, in the preparation of chrome yellow and other lead
compounds, and mixed with lead peroxide (obtained by treatment of red
lead with nitric acid) in the manufacture of lucifer matches. Apart from
risk from nitrous fumes (common to all these salts) there is risk also of
chronic lead poisoning.
_Nitrate of iron_ (Fe(NO₃)₂), forming green crystals, is made by
dissolving sulphide of iron or iron in cold dilute nitric acid. The
so-called nitrate of iron commonly used in dyeing consists of basic
sulphate of iron (used largely in the black dyeing of silk).
_Copper nitrate_ (Cu(NO₃)₂), prepared in a similar way, is also used in
dyeing.
_Mercurous nitrate_ (Hg₂(NO₃)₂) is of great importance industrially, and
is produced by the action of cold dilute nitric acid on an excess of
mercury. It is used for ‘carotting’ rabbit skins in felt hat making, for
colouring horn, for etching, and for forming an amalgam with metals, in
making a black bronze on brass (art metal), in painting on porcelain, &c.
_Mercuric nitrate_ (Hg(NO₃)₂) is made by dissolving mercury in nitric
acid or by treating mercury with excess of warm nitric acid. Both the
mercurous and mercuric salts act as corrosives and are strongly poisonous
(see also Mercury and Hat Manufacture).
_Nitrate of silver_ (AgNO₃) is obtained by dissolving silver in nitric
acid and is used commercially as a caustic in the well-known crystalline
pencils (lunar caustic). Its absorption into the system leads to
accumulation of silver in the skin—the so-called argyria (see Silver).
Such cases of chronic poisoning are recorded by Lewin.[7] Argyria occurs
among photographers and especially in the silvering of glass pearls owing
to introduction of a silver nitrate solution into the string of pearls by
suction. In northern Bohemia, where the glass pearl industry is carried
on in the homes of the workers, I saw a typical case. The cases are now
rare, as air pumps are used instead of the mouth.
_Sodium nitrite_ (NaNO₂) is obtained by melting Chili saltpetre with
metallic lead in cast-iron vessels. The mass is lixiviated and the
crystals obtained on evaporation. The lead oxide produced is specially
suitable for making red lead. Cases of lead poisoning are frequent and
sometimes severe. Roth[8] mentions a factory where among 100 employed
there were 211 attacks in a year.
_Amyl nitrite_ (C₅H₁₁NO₂) is made by leading nitrous fumes into iso-amyl
alcohol and distilling amyl alcohol with potassium nitrite and sulphuric
acid. It is a yellowish fluid, the fumes of which when inhaled produce
throbbing of the bloodvessels in the head and rapid pulse.
For other nitric acid compounds see the following section on Explosives
and the section on Manufacture of Tar Products (Nitro-benzene, &c.).
Explosives
Numerous explosives are made with aid of nitric acid or a mixture of
nitric and sulphuric acids. Injury to health and poisoning—especially
through development of nitrous fumes—can be caused. Further, some
explosives are themselves industrial poisons, especially those giving off
volatile fumes or dust.
The most important are:
_Fulminate of mercury_ (HgC₂N₂O₂) is probably to be regarded as the
mercury salt of fulminic acid, an isomer of cyanic acid. It is used
to make caps for detonating gunpowder and explosives, and is made by
dissolving mercury in nitric acid and adding alcohol. The heavy white
crystals of mercury fulminate are filtered off and dried. Very injurious
fumes are produced in the reaction, containing ethyl acetate, acetic
acid, ethyl nitrate, nitrous acid, volatile hydrocyanic acid compounds,
hydrocyanic acid, ethyl cyanide, cyanic acid; death consequently can
immediately ensue on inhalation of large quantities. The fulminate is
itself poisonous, and risk is present in filtering, pressing, drying,
and granulating it. Further, in filling the caps in the huts numerous
cases of poisoning occur. Heinzerling thinks here that mercury fumes are
developed by tiny explosions in the pressing and filling. In a factory in
Nuremburg 40 per cent. of the women employed are said to have suffered
from mercurial poisoning. Several cases in a factory at Marseilles are
recorded by Neisser.[9] In addition to the risk from the salt there is
even more from nitrous fumes, which are produced in large quantity in the
fulminate department.
_Nitro-glycerin_ (C₃H₅(O—NO₂)₃, dynamite, explosive
gelatine).—Nitro-glycerin is made by action of a mixture of nitric and
sulphuric acids on anhydrous glycerin. The method of manufacture is as
follows (see fig. 10): glycerin is allowed to flow into the acid mixture
in leaden vessels; it is agitated by compressed air and care taken that
the temperature remains at about 22° C., as above 25° there may be risk.
The liquid is then run off and separates into two layers, the lighter
nitro-glycerin floating on the top of the acid. The process is watched
through glass windows. The nitro-glycerin thus separated is run off,
washed by agitation with compressed air, then neutralised (with soda
solution) and again washed and lastly filtered. The acid mixture which
was run off is carefully separated by standing, as any explosive oil
contained in it will rise up. The waste acid freed from nitro-glycerin is
recovered in special apparatus, being denitrified by hot air and steam
blown through it. The nitrous fumes are condensed to nitric acid. The
sulphuric acid is evaporated.
_Dynamite_ is made by mixing nitro-glycerin with infusorial earth
previously heated to redness and purified.
_Blasting gelatine_ is made by dissolving gun cotton (collodion wool,
nitro-cellulose) in nitro-glycerin. Both are pressed into cartridge shape.
Nitro-glycerin itself is a strong poison which can be absorbed both
through the skin and from the alimentary canal. Kobert describes a case
where the rubbing of a single drop into the skin caused symptoms lasting
for ten hours. Workmen engaged in washing out nitro-glycerin from the
kieselguhr earth, having in doing so their bare arms immersed in the
liquid, suffered. Although it be granted that nitro-glycerin workers
become to a large extent acclimatised, cases of poisoning constantly
occur in explosives factories referable to the effect of nitro-glycerin.
Persons mixing and sieving dynamite suffer from ulcers under the nails
and at the finger-tips which are difficult to heal. Further, where the
apparatus employed is not completely enclosed nitrous fumes escape and
become a source of danger. Formerly this danger was constantly present
in the nitrating house where nitration was effected in open vessels.
Now that this is usually done in closed nitrating apparatus with glass
covers the danger is mainly limited to the acid separating house, wash
house, and especially the room in which denitration of the waste acids is
effected.
[Illustration: FIG. 10.—Preparation of Nitro-glycerin. Nitrating Vessel
(_after Guttmann_)
A Glycerine reservoir; C Fume flue; D Acid supply pipe; E, G Compressed
air supply; H, J Cooling coil.]
A fatal case in a nitro-glycerin factory was reported in 1902 where,
through carelessness, a separator had overflowed. The workman who tried
to wash away the acid with water inhaled so much of the nitrous fumes
that he succumbed sixteen hours later.
Other cases of poisoning by nitrous fumes occurring in the denitrating
department are described in detail in the section on the use of nitric
acid.
One of these occurred to a man forcing dilute nitric acid from an
earthenware egg by means of compressed air into a washing tower. The egg
burst and broke an acid tank. The workman died on the following day.
A fatal case occurred in a dynamite factory in cleaning out a storage
tank for waste acid in spite of previous swilling and ventilation.
_Gun cotton_ (_pyroxyline_) and its use.—Pyroxyline is the collective
name for all products of the action of nitric acid on cellulose (cotton
wool and similar material); these products form nitric acid ester of
cellulose (nitro-cellulose).
Gun cotton is formed by the action of strong nitric acid on cellulose
(cotton wool). A mixture of sulphuric and nitric acids is allowed to act
on cotton wool (previously freed from grease, purified, and dried), with
subsequent pressing and centrifugalising. In the nitrating centrifugal
machine (in the Selvig-Lange method) both processes are effected at the
same time.
The interior of this apparatus is filled with nitric acid, cotton wool is
introduced, the acid fumes exhausted through earthenware pipes, and the
remainder of the acid removed by the centrifugal machine; the nitrated
material is then washed, teazed in teazing machines, again washed,
neutralised with calcium carbonate, again centrifugalised, and dried.
Since drying in drying stoves is a great source of danger of explosion,
dehydration is effected with alcohol, and the gun cotton intended for
the production of smokeless powder carried directly to the gelatinising
vessels (see Smokeless Powder).
Gun cotton, apart from its use for smokeless powder, is pressed in prisms
and used for charging torpedoes and sea mines.
_Collodion cotton_ is a partially nitrated cellulose. It is prepared
generally in the same way as gun cotton, except that it is treated with
a more dilute acid. It is soluble (in contradistinction to gun cotton)
in alcohol-ether, and the solution is known as collodion (as used in
surgery, photography, and to impregnate incandescent gas mantles). Mixed
with camphor and heated collodion forms celluloid.
In Chardonnet’s method for making artificial silk collodion is used by
forcing it through fine glass tubes and drawing and spinning it. The
alcohol-ether vapours are carried away by fans and the spun material is
de-nitrated by ammonium sulphide.
_Smokeless powder_ is a gun cotton powder—that is gun cotton the
explosive power of which is utilised by bringing it into a gelatinous
condition. This is effected by gelatinising the gun cotton with
alcohol-ether or acetone (sometimes with addition of camphor, resin,
&c.). A doughy, pasty mass results, which is then rolled, washed, dried,
and pressed into rods. Nobel’s nitroleum (artillery powder) consists half
of nitro-glycerin and half of collodion cotton. In the production of gun
cotton and collodion cotton the workers are affected and endangered by
nitric and nitrous fumes unless the nitrating apparatus is completely
airtight.
Erosion of the incisor teeth is general, but use of the new nitrating
apparatus, especially of the nitrating centrifugal machines already
described, has greatly diminished the evil. In making collodion,
celluloid and artificial silk, in addition to the risks referred to
in the production of gun cotton, the vapour from the solvents, ether,
alcohol, acetone, acetic-ether, and camphor, comes into consideration,
but there is no account of such poisoning in the literature of the
subject.
Other explosives which belong to the aromatic series are described in the
chapter on Tar Derivatives, especially picric acid.
PHOSPHORUS AND PHOSPHORUS MATCHES
The total production of _phosphorus_ is not large. Formerly it was
prepared from bone ash. Now it is made from phosphorite, which, as
in the super-phosphate industry, is decomposed by means of sulphuric
acid, soluble phosphate and calcium sulphate being formed; the latter
is removed, the solution evaporated, mixed with coal or coke powder,
distilled in clay retorts, and received in water.
Phosphorus is also obtained electro-chemically from a mixture of
tricalcium phosphate, carbon, and silicic acid, re-distilled for further
purification, and finally poured under water into stick form.
_Red phosphorus_ (amorphous phosphorus) is obtained by heating yellow
phosphorus in the absence of air and subsequently extracting with carbon
bisulphide.
_Phosphorus matches_ are made by first fixing the wooden splints in
frames and then dipping the ends either into paraffin or sulphur which
serve to carry the flame to the wood. Then follows dipping in the
phosphorus paste proper, for which suitable dipping machines are now
used. The phosphorus paste consists of yellow phosphorus, an oxidising
agent (red lead, lead nitrate, nitre, or manganese dioxide) and a binding
substance (dextrine, gum); finally the matches are dried and packed.
_Safety matches_ are made in the same way, except that there is no
phosphorus. The paste consists of potassium chlorate, sulphur, or
antimony sulphide, potassium bichromate, solution of gum or dextrine,
and different admixtures such as glass powder, &c. These matches are
saturated with paraffin or ammonium phosphate. To strike them a special
friction surface is required containing red phosphorus, antimony
sulphide, and dextrine. In the act of striking the heat generated
converts a trace of the red phosphorus into the yellow variety which
takes fire.
Danger to health arises from the poisonous gases evolved in the
decomposition of the calcined bones by sulphuric acid. When phosphorus is
made from phosphorite the same dangers to health are present as in the
production of super-phosphate artificial manure, which is characterised
by the generation of hydrofluoric and fluosilicic acids. In the
distillation of phosphorus phosphoretted hydrogen and phosphorus fumes
may escape and prove dangerous.
Industrial poisoning from the use of white phosphorus in the manufacture
of matches has greater interest than its occurrence in the production
of phosphorus itself. Already in 1845 chronic phosphorus poisoning
(phosphorus necrosis) had been observed by Lorinser, and carefully
described by Bibra and Geist in 1847. In the early years of its use
phosphorus necrosis must have been fairly frequent in lucifer match
factories, and not infrequently have led to death. This necessitated
preventive measures in various States (see Part III); cases became fewer,
but did not disappear altogether.
Especially dangerous is the preparation of the paste, dipping, and
manipulations connected with drying and filling the matches into boxes.
According to the reports of the Austrian factory inspectors there are
about 4500 lucifer match workers in that country, among whom seventy-four
cases of necrosis are known to have occurred between the years 1900 and
1908 inclusive.
Teleky[1] considers these figures much too small, and from inquiries
undertaken himself ascertained that 156 cases occurred in Austria
between 1896 and 1906, while factory inspectors’ reports dealt with only
seventy-five. He was of opinion that his own figures were not complete,
and thinks that in the ten years 1896 to 1905 there must have been from
350 to 400 cases of phosphorus necrosis in the whole of Austria. Despite
strict regulations, modern equipment of the factories, introduction of
improved machinery, and limitation of the white phosphorus match industry
to large factories, it has not been possible to banish the risk, and the
same is true of Bohemia, where there is always a succession of cases.
Valuable statistics of phosphorus necrosis in Hungary are available.[2]
In 1908 there were sixteen factories employing 1882 workers of whom
30 per cent. were young—children even were employed. The industry is
carried on in primitive fashion without hygienic arrangements anywhere.
It is strange that, notwithstanding these bad conditions, among a large
number of the workers examined only fourteen active cases were found, in
addition to two commencing, and fifteen cured—altogether thirty-one cases
(excluding fifty-five cases in which there was some other pathological
change in the mouth). Altogether ninety-three cases since 1900 were
traced in Hungary, and in view of the unsatisfactory situation preventive
measures, short of prohibition of the use of white phosphorus, would be
useless.
In England among 4000 lucifer match workers there were thirteen cases
in the years 1900 to 1907 inclusive. Diminution in the number was due
to improved methods of manufacture and periodical dental examination
prescribed under Special Rules.
Phosphorus necrosis is not the only sign of industrial phosphorus
poisoning, as the condition of fragilitas ossium is recognised.[3]
From what has been said it is evident that preventive measures against
phosphorus poisoning, although they diminish the number, are not able to
get rid of phosphorus necrosis, and so civilised States have gradually
been driven to prohibit the use of white phosphorus (for the history of
this see Part III).
Use of chrome salts (especially potassium bichromate) in the preparation
of the paste causes risk of poisoning in premises where ‘Swedish’
matches are made. Attention has been called to the frequency of chrome
ulceration.[4] The paste used consists of 3-6 per cent. chrome salt, so
that each match head contains about ½ mg. Wodtke found among eighty-four
workers early perforation of the septum in thirteen. Severe eczema also
has been noted.
It is even alleged that red phosphorus is not entirely free from danger.
Such cachexia as has been noted may be referable to the absorption of
potassium chlorate.
Other Uses of Phosphorus and Compounds of Phosphorus
Isolated cases of phosphorus poisoning have been observed in the
manufacture of phosphor-bronze. This consists of 90 parts copper, 9 parts
tin, and 0·5 to 0·75 phosphorus.
_Sulphides of phosphorus_ (P₂S₅, P₄S₃, P₂S₃) are made by melting together
red phosphorus and sulphur. They make a satisfactory substitute for the
poisonous yellow phosphorus and are considered non-poisonous, but the
fact remains that they give off annoying sulphuretted hydrogen gas.
_Phosphoretted hydrogen gas_ (PH₃) rarely gives rise to industrial
poisoning. It may come off in small amounts in the preparation of
acetylene and in the preparation of, and manipulations with, white
phosphorus. It is stated that in acetylene made of American calcium
carbide 0·04 per cent. of phosphoretted hydrogen is present, and in
acetylene from Swedish calcium carbide 0·02 per cent.; Lunge and
Cederkreutz found an acetylene containing 0·06 per cent. These amounts
might cause poisoning if the gas were diffused in confined spaces.
Poisoning, in part attributable to phosphoretted hydrogen gas, is brought
about through ferro-silicon (see under Ferro-silicon).
Superphosphate and Artificial Manure
_Superphosphate_, an artificial manure, is prepared from various
raw materials having a high proportion of insoluble basic calcium
phosphate (tricalcium phosphate), which by treatment with sulphuric
acid are converted into the soluble acid calcium phosphate (monocalcium
phosphate) and calcium sulphate. Mineral substances such as phosphorites,
coprolites, guano, bone ash, &c., serve as the starting-point. Chamber
acid, or sometimes the waste acid from the preparation of nitro-benzene
or purification of petroleum, are used in the conversion. The raw
materials are ground in closed-in apparatus, under negative pressure,
and mixed with the sulphuric acid in wooden lead-lined boxes or walled
receptacles. The product is then stored until the completion of the
reaction in ‘dens,’ dried, and pulverised in disintegrators.