By the _roast and reaction method_ a par_Lead poisoning and lead absorption

converted into oxide and sulphate of lead with access of air.

Subsequently, on shutting off the air-supply and increasing the

temperature, a reaction takes place. The sulphur in the unchanged

sulphide combines with the oxygen of the oxide and sulphate to form

sulphur dioxide, which is carried away by the draught into the bricked

flue, leaving metallic lead behind. The process is carried on in a

reverberatory or open-hearth furnace.

In the _roast and reduction method_ the first portion of the process

is carried out in a reverberatory furnace, the galena being roasted

pretty completely to lead oxide and sulphate, which are then--usually

in a blast furnace--reduced to the metallic state with coke and other

reducing agents, such as iron.

By the _precipitation process_ galena was decomposed at a high

temperature by means of metallic iron, forming a mixture of iron and

lead sulphide. This method was only applicable to rich lead ores, and

is now given up.

The three methods are hardly ever independent of one another, as the

rich slag or residues, for instance, which are obtained by the first

method are retreated by the second, and the second is, as has been

stated, almost always combined with the first.

On tapping the blast or reverberatory furnace, the lead is drawn

off into a lead well or sump, from which, when cool, it is ladled

into moulds, while the slag is run into movable metal pots or along

specially-prepared channels. The slag run off from the reverberatory

furnace contains much lead locked up as silicate, which requires to be

retreated, usually in the blast furnace. During the roasting process

much raking of the material is necessary. The slag from the blast

furnace should contain less than 1 per cent. of lead.

On the Continent and in America, the Huntingdon-Heberlein process has

been extensively adopted, with lessened incidence of poisoning, the

result of mechanical methods of working, obviating hand labour, and the

low temperature (diminishing risk from lead fume) at which the roasting

is carried on. In this process the crushed ore is desulphurized by

first mixing with lime and heating in presence of air in a revolving

furnace, provided with automatic rabble, at moderate temperature (about

700° C.). Subsequently the roasted material is conveyed from closed

bins, into which it falls automatically, by dust-proof elevators to

a converter, in which atmospheric air at slight pressure is forced

through it. The agglomerated mass so formed, when tipped out of the

converter (in doing which there is risk from dust), is well damped,

broken by hand, and charged with coke in the usual way into the blast

furnace.

In some lead-smelting works the material arrives on the premises

in the form of ingots of base bullion--_i.e._, impure lead rich in

silver--the product of previous smelting of the ore where it is mined

in Australia or Spain. And one of the main objects of the blast-furnace

smelting of galena in the factory is to produce a base bullion rich

in precious metals. The lead so obtained requires further softening

or refining to get rid of copper, antimony, arsenic, and tin. This

is effected in a reverberatory furnace, first at a low temperature

to allow of formation of furnace dross, which is removed through

the working doors, and secondly with increase of heat and access of

air to oxidize, in the order named, the tin, arsenic, and antimony.

Finally the lead is tapped into kettles or pots. If free from silver,

such lead, when poured into moulds, is ready for the market; but if

rich in silver, it is treated for the recovery of that metal either

by (_a_) Pattinson’s process, depending on the higher temperature of

crystallization of lead than of an alloy of lead and silver, which

enables a separation of one from the other to be made by a process

of ladling the crystalline from the liquid portion; or, much more

commonly, by (_b_) Parkes’s process, depending on the formation,

on addition of zinc to a pot of molten lead, of crusts consisting

of an alloy of silver, lead, and zinc. The crusts obtained in the

latter process, after cooling, are broken up, placed in a crucible,

and the zinc driven off at a temperature of 1,000° C. in a dezincing

Faber du Faur retort. The rich bullion, retained either in the last

kettle by the Pattinson process, or remaining in the crucible after

dezincing, next undergoes cupellation--_i.e._, exposure to a blast

of air in a furnace. The lead is oxidized into litharge, which drops

into a receptacle below the furnace, leaving the silver behind. In all

lead-smelting works the draught from the furnace carries much dust of

ore and fuel, and fume, consisting of sulphide, sulphate, and oxides of

lead, into the flues. The dust is easily collected in dust chambers,

but the fume requires ducts of great length--sometimes a mile or

more--in which to deposit.

_Dangers and Prevention._--The risk from dust in general labouring

work, in depositing the ores in bins, in removing them to, and charging

them into, the furnace, can only be controlled by watering, preferably

by a spray. From the blast furnace lead fume and carbon monoxide may

escape at the point where charging is done, if there is back pressure

from blockage in the flues, or if the furnace blast is not working

perfectly. In tapping the lead and in manipulations such as charging,

drossing, and skimming, conducted through the doors of furnaces of all

descriptions, hoods, extending at the sides down to the floor level,

require to be arranged over the working doors, and connected either

with ducts passing vertically through the roof or directly with the

exhaust created in the furnace or flue itself. Dross and skimmings

removed through the working doors should be received into iron trolleys

capable of being covered, and not be allowed to fall on to the floors,

to be shovelled up later on to barrows. Before such dross or slag from

reverberatory furnaces is broken up for further treatment it should be

well watered.

Lead absorption among the men actually employed in the Pattinson

and Parkes’s processes is comparatively rare, as the temperature of

the molten metal does not exceed 450° to 500° C. When, however, the

zinc-silver-lead and gold alloy is removed for treatment in special

furnaces for distillation off of the zinc, prior to cupellation, the

lead from the Parkes’s pot, now free from silver, but containing traces

of zinc, antimony, and other impurities, is run in some works into

what are termed “market pots” for a final refining. Air and steam are

blown through to oxidize the impurities. The pot is skimmed twice,

the first dross containing antimony, etc., and the second a fine dust

consisting of lead (60 per cent.) and zinc. The risk of poisoning at

this point is considerable, although an exhaust fan connects up the

cover of the pot with a cyclone separator, to carry away the fume when

the steam is blown through. In other works this dezincing is done in

a refining furnace, the material being then in a slaggy state, thus

hindering development of fumes. After the condensation of the zinc in

the distillation of the silver-lead and zinc crust the cover of the

pot is raised, and the remaining metal, containing 80 per cent. of

lead at a temperature of about 2,000° F., is ladled out into moulds

for treatment in the cupelling furnace. The temperature at which this

ladling operation has to be done makes the work impossible for those

unaccustomed to it. Exhaust ventilation in the operation of emptying

the pot, and cutting off the heat by a water-cooled jacket, suggest

themselves as means to combat the undoubted risk.

In cupellation the temperature is high (about 2,000° C.), and fume will

escape from the working door and from the opening where the rich lead

is fed into the furnace. The danger here is sufficiently recognized

by hoods and ducts placed in front of the furnace, but the draught,

unless the ducts are connected up with a high-pressure fan, may prove

inadequate to carry away all the fume.

Flue-cleaning, carried out usually at quarterly or half-yearly periods,

is dusty work, as much of the dust is in so fine a state of division as

to repel contact with water.

Smelting of other metals when the ores contain appreciable amounts

of lead is equally productive of plumbism. Thus, in the year 1901

fourteen cases were reported from an iron works for the manufacture of

spiegeleisen, the ore (now no longer used) coming from Greece[2]. In

previous years it would appear to have been even greater. A remarkable

feature of all the reported cases from this factory was that the form

assumed was colic, and never paralysis. The poisoning was due to

vaporization of the molten lead by the very high temperature to which

it was raised as the molten iron flowed out of the furnace on tapping.

The danger from fume was limited to the first few feet of the channel,

as the heavier molten lead gravitated down between loose brickwork into

a pit. Dust collected above the point where the furnace was tapped

contained 39·77 per cent. of lead monoxide, and the flue dust 4·22 per

cent.[3]. A flannel respirator worn once only by one of the furnace men

contained lead equal to 16 milligrammes of lead monoxide. In 1906 three

cases were reported in the extraction of copper. The persons affected

were employed in charging ore into the cupola[4].

Heavy incidence of poisoning (twelve cases in two months) in a smelting

works (now closed) led to examination of sixteen men. The gums of

only one man were free of a blue line--in most it was particularly

dense--eight were anæmic, one had paralysis of the wrists, and five

others weakness. Analysis of the air was made at different points

in the factory by the chemist of the works, G. D. Cowan, with the

following results:

The samples from the cupola were taken from inside the hood (about

5 feet above the men’s heads). The gas was filtered through

cotton-wool, so that all solid particles were retained, and the

remaining gas was treated separately. The solid particles will be

called “dust,” and the gas, after filtration, “fume.”

The cupola samples on being examined gave--

Dust, first sample 0·08152 grain of lead per cubic foot.

„ second sample 0·07297 „ „ „

Fume, first sample } 0·00526 „ „ „

„ second „ }

The samples from the lead well were taken 12 inches above the molten

metal at the end of the lead siphon, and gave the following results:

Dust 0·05653 grain per cubic foot.

Fume Nil.

The briquetting machine samples were taken from the platform where

all the ore and fluxes are mixed before briquetting.

The results obtained here were as follows:

Dust 0·95715 grain of lead per cubic foot.

Fume, or fine dust that passed

through filter 0·01314 „ „ „

The reason for these high results was owing to dust raised when

waggons of ore were tipped prior to mixing.

Assuming that 20 cubic inches of air pass in and out of the lungs at

each respiration, a man in eight hours would inhale and exhale 94·4

cubic feet. This amount of air, inhaled at the position in the cupola

where the sample was taken, would contain 7·3818 grains of lead; at

the lead well, 5·3064 grains; and at the briquetting machines, 91·5953

grains. Although the condition of the air where the men actually worked

must have contained much less than these amounts, the analyses quite

serve to explain the heavy incidence.

Collis[5] quotes the following analysis of dust and fumes from Hofman’s

“Metallurgy of Lead.”

LEAD SMELTING: ANALYSES OF DUST AND FUMES (FROM HOFMAN’S “METALLURGY OF

LEAD”).

+--------------------------------+---------------------------------+

| | Percentage of-- |

| +------+------+-----+------+------+

| | Ar- | nious| |Monox-| Sul- |

+--------------------------------+------+------+-----+------+------+

| (1) | (2) | (3) | (4) | (5) | (6) |

|All dust collected in ten years,| -- | -- | 25·6| -- | -- |

| Downcomers of eleven blast | -- | -- | 47·5| -- | -- |

| Roof of blast-furnace building| -- | -- | 27·1| -- | -- |

| Slag pot while boiling | -- | 4·8 | -- | 41·0 | 26·2 |

| Reverberatory settling furnace| 2·3 | -- | -- | 31·0 | -- |

| Friedrichshütte, Silesia | -- | -- | -- | 62·8 | -- |

| { A | 7·5 | -- | 26·2| -- | -- |

| Freiberg, Saxony { B | 37·5 | -- | 21·3| -- | -- |

| { C | 46·4 | -- | 16·2| -- | -- |

| Pribram, Bohemia | -- | 1·0 | -- | 45·5 | -- |

+--------------------------------+------+------+-----+------+------+

Collis[6] estimated the attack rate in lead-smelting works at 30, and

in spelter works at 10, per 1,000 per annum. In one factory he found

it 80 per 1,000, and in a spelter works five cases occurred in a few

months among seven workers.

The distribution of the reported cases from year to year was as follows:

+--------------+-----+-----+-----+-----+-----+-----+-----+

| Process. |1900.|1901.|1902.|1903.|1904.|1905.|1906.|

+--------------+-----+-----+-----+-----+-----+-----+-----+

|Lead smelting | 21 | 26 | 13 | 13 | 7 | 10 | 16 |

|Desilverizing | 1 | 3 | 9 | 10 | 16 | 6 | 9 |

|Spelter | 5 | 11 | 3 | 4 | 4 | 5 | 9 |

|Other (copper,| 7 | 14 | 3 | 10 | 6 | 3 | 4 |

| +-----+-----+-----+-----+-----+-----+-----+

| | 34 | 54 | 28 | 37 | 33 | 24 | 38 |

+--------------+-----+-----+-----+-----+-----+-----+-----+

+--------------+-----+-----+-----+-----+-----+------+

| Process. |1907.|1908.|1909.|1910.|1911.|Total.|

+--------------+-----+-----+-----+-----+-----+------+

|Lead smelting | 21 | 31 | 28 | 21 | 33 | 240 |

|Desilverizing | 4 | 3 | 6 | -- | 3 | 70 |

|Spelter | 2 | 31 | 25 | 12 | 11 | 122 |

|Other (copper,| 1 | 5 | 7 | 1 | 1 | 62 |

| +-----+-----+-----+-----+-----+------+

| | 28 | 70 | 66 | 34 | 48 | 494 |

+--------------+-----+-----+-----+-----+-----+------+

=Spelter (Zinc) Manufacture.=--Lead is present in zinc ores in a

proportion of from 1 to 10 per cent. (usually 3 per cent.). Despite

this small proportion, incidence of chronic plumbism among those

engaged in the manufacture is high, as in the present state of

knowledge the lead fume given off in distillation of the zinc cannot

be efficiently removed. Blende (zinc sulphide) is first calcined, and

the residue, after mixture with calamine (zinc ashes) and anthracite,

forms the charge for the furnace. The retorts are arranged in long

rows one above the other, and frequently back to back in the furnace,

so that there may be 250 or more to each furnace, and of the furnaces

there may be several in a shed. Attached to the retort is a fireclay

receptacle (condenser) into which the zinc distils, and an iron nozzle

(prolong) to prevent oxidation in the condenser. While distillation

goes on the carbonic oxide gas evolved burns brightly, tinged with the

greenish-white colour imparted by the zinc. The products of combustion,

with traces of lead fume from the hundreds of prolongs, are discharged

into the atmosphere of the sheds, where temperature is high. The

latest design of prolongs, however, has an exit at which the products

of combustion escape near the furnace, so that the greater portion

pass up into the ventilating hoods. Periodically--three times to each

charge--the workman removes the prolong, ladles out such zinc as has

condensed, and pours it into moulds. Finally, when distillation is

completed, the contents of the retorts are raked out, and it is in the

fuming hot residues so deposited on the floors that much of the danger

arises. In distilling furnaces of modern design the hot residues fall

through openings in the window of the furnaces into “pockets,” in

which they cool off considerably before they are drawn out into iron

skips. In another form of furnace used in the manufacture of spelter

(Silesian), the workman after charging can leave the furnace until the

time for tapping arrives. The two operations involve work for six hours

a day only.

_Dangers and Prevention._--During distillation the detrimental effect

of a current of air (formation of zinc oxide) on the zinc is an

obstacle to the removal of the fume by exhaust ventilation locally

applied over the prolongs of the condensers. Exhaust ventilation of

a kind can, however, be arranged, except under unfavourable weather

conditions, by erecting hoods of material such as galvanized iron right

across the roof of the shed over, and parallel with, the furnaces, up

which the heated current of air from the furnaces travels. Lofty, roomy

sheds assist materially in the escape of the fumes. Various forms of

modification in the condensers, designed to lessen escape of fume, and

so recover more zinc, are being tried.

Samples of fume condensed as a grey powder, and collected by Collis

from different kinds of prolongs, showed 1·3 to 2·7 per cent.[7]

of metallic lead respectively, and a sample of dust deposited from

material containing 10 per cent. of lead, 3·25 per cent.[8].

=Manufacture of Red and Orange Lead and Litharge.=--These processes

are frequently carried on as part of lead-smelting works. Red lead is

produced by oxidation, first, of metallic pig-lead, in a reverberatory

furnace at dull red heat, into massicot (yellow monoxide). During the

process the material is constantly raked. The massicot is withdrawn

from the furnace, and subsequently, after drying and sieving, is again

subjected to similar treatment at slightly lower temperature. Orange

lead is made by treating white lead in the manner described.

During the ten years 1900-1909 the number of reported cases from the

manufacture of red lead was 108, of which 47 were attributed to work at

the furnaces, 43 to packing and sieving, and 16 occurred among general

labourers, part of whose duty it was to sweep up the floors. Collis

estimates the attack rate in the five years 1905-1909, in a certain

number of factories employing 171 persons, at 50 per 1,000. Reference

to the table on p. 48 shows that the proportion of those suffering from

encephalopathy is higher than in any other industry--an observation

previously noted by Layet[9].

_Dangers and Prevention._--Danger is practically limited to escape

of dust in (1) raking the charge out from the hearth on to iron

trolleys, (2) sieving, and (3) packing. In all these operations exhaust

ventilation is essential, and for sieving and packing the installation

requires to be designed with especial care, so as to be able to keep

within the sphere of the exhaust the spading and shovelling of the

material, in very fine state of division, into the cask. Sometimes the

material is elevated from pits, and eventually packed by mechanical

means into barrels resting on a jolter. Unless the elevators are

quite dust-proof, and the collar hermetically seals the connection of

the shoot with the barrel, the vibration of the heavy machinery and

pressure of air inside the casing will cause dust to escape.

Red lead can be, and is, now made on an extensive scale in such a way

that all operations, from commencement with pig-lead to the final

packing, are carried out by mechanical means so entirely closed in that

the worker does not come into contact with the material. The person

who then may be affected is the fitter attending to repairs of the

machinery. The pig-lead is melted, stirred, and mixed in a covered-in

melting-pot. The massicot which is formed is drawn off by an exhaust

into a hopper, from the bottom of which it is fed mechanically on to

the floor of the furnace. Mechanical rabbles stir it from the centre

to the outside of the furnace floor, from where it is conveyed, under

negative pressure, to the hopper of a grinding mill. From here it is

again similarly fed into another furnace. The exhaust pipe from this

furnace collects the finished product, carrying it mechanically to a

hopper which automatically feeds the red lead into casks. Negative

pressure throughout prevents escape of dust.

=Manufacture of Litharge.=--Pig-lead is placed in a cupellation

furnace, and constantly stirred and raked over to cause entire

oxidation, and then is either raked out or run out from the furnace

hearth into moulds, and allowed to cool in the form of large balls.

These balls, of a roughly crystalline nature, are deposited on the

floor, where they are exposed to the air. Disintegration is accelerated

by breaking up the large fragments by hand. Subsequently the material

is placed in a disintegrator for fine division and packed.

_Dangers and Prevention._--Manufacture of litharge may cause a greater

amount of dust than any other process with which we are familiar. The

nature of the operations is such that it is impossible at all stages

to control this dust. Danger is greatest in the early operations of

shovelling up the disintegrated powdery material from the floors into

receptacles, and in discharging the contents into the disintegrating

machine. The work is heavy, and a respirator is with difficulty worn.

A movable hood attached to a flexible duct in connection with an

exhaust which could be moved from place to place on the floor suggests

itself, but when tried it has not effectively controlled the dust,

owing to both the trouble involved and the difficulty of bringing

the exhaust near enough to the work. When once the material reaches

the disintegrator, exhaust over the hopper, and in connection with

the enclosed sifter and grinder and packing machine, can readily be

secured. Bins should be provided for the litharge lumps, so as to

avoid trampling the powder underfoot, and covered barrows for removing

the semi-powdered material. Alternation of employment lessens risk,

and should be always arranged. In any new plant the possibility of

automatic methods of carrying out the process as far as possible should

be considered.

=Sheet Lead and Lead Piping.=--This industry also is not infrequently

carried out on smelting premises. To make lead piping, molten refined

lead is run into a cylinder containing an adjustable mandrel in its

centre. The cylinder is forced by hydraulic pressure against a hollow

ram having an adjustable orifice to form the desired thickness of pipe.

In the case of sheet lead the thick plates are gradually reduced to the

desired thickness by pressure of heavy steel rollers.

_Dangers and Prevention._--Little risk attaches to handling the clean

sheet lead or drawn lead. Danger is in the early stages. Old oxidized

lead piping, lead cisterns, tea lead, old accumulator plates, etc., lie

in heaps on the premises. These cannot be handled without generation

of dust. When melted and stirred, copious fumes arise, carrying up

dust, from which, and from that raised in drossing the surface of the

metal, absorption of lead is inevitable unless the melting-pot is

fully protected from side-draughts and provided with a hood and duct

leading into the main chimney-stack. Doors in front of the hood serve

still further to confine the fumes. The skimmings from the pot require

to be placed in a receptacle under the hood. Of 109 cases reported

in the ten years 1900-1909, operations at the melting-pot accounted

for at least 47. We are in agreement with Dixon Mann, who remarks:

“Workers in metallic lead do not suffer unless they are frequently in

the presence of large quantities of the molten metal, or inhale fine

particles of solid lead or its oxide whilst manipulating old metal.

Lead, though not usually classed amongst the volatile metals, is

capable of volatilization at a high temperature, and in the form of

vapour may be taken into the system through the respiratory tract, and

also into the stomach. One of the worst cases of chronic lead poisoning

I ever saw was that of a man who bought the sheets of lead linings of

old tea-chests, and melted them down into pig-lead. He did the work in

a small room, without any contrivance for ventilation, and attended to

the whole process himself”[10].

=Letterpress Printing.=--In this industry account has to be taken of

contact with--

1. Molten lead in (_a_) casting the type in different kinds of

machines, including the monotype and linotype; (_b_) in stereotyping;

and (_c_) in recasting into moulds the line or single type after it

has been once used, together with débris from the stereo machine and

sweepings from the floor.

2. Metallic lead in handling and dressing the type, and subsequent

use of it by the compositor. The type metal itself usually consists

of--Lead, 75 per cent.; antimony, 23 per cent.; and tin, 2 per cent.

During the ten years 1900-1909, 200 cases were reported--92

compositors, 71 stereotype and linotype operators, and 37 in subsidiary

processes, mainly in the casting-room. Thus, apparently, operations

involving contact with molten metal are more likely to cause lead

poisoning than actual handling.

_Type-Casting._--In letter founding and in the monotype letter-casting

machine the molten metal, heated by a coal fire in the former and

Bunsen burner in the latter, at regular intervals fills the matrices at

a point where it is cooled by a jet of compressed air, and the formed

letter is then mechanically ejected into a receptacle. The temperature

of the molten metal has to be carefully regulated, and does not usually

rise above 400° to 450° C.--a temperature at which it is extremely

doubtful if lead fume can be produced. Sommerfeld[11] states that in 60

cubic metres of air aspirated close to a type-casting machine no trace

of lead was found, because vaporization does not take place below 550°

C. Such skimming as must occasionally be made of the small surface

of molten metal is in a slaggy state, and does not appear to contain

much oxide. This is deposited usually in a small box and removed to be

remelted once a day. What fume, often of unpleasant odour, is noted is

probably due to acroleic acid vapour from the grease and dirt.

The letters having been cast, the type may be rubbed on sandstone or

on a file, by which small quantities of metallic dust are given off;

set up on setting-boards so that all letters face the same way (work on

which female young persons are usually engaged); certain portions of

letters undercut so as to make them lie perfectly parallel; dressed,

planed, and examined, so as to be of precisely the same height; and

finally assorted into founts and packed in the warehouse. In all these

operations the fingers necessarily get blackened by contact, and there

must be slight dislodgment of metal particles to account for the cases

reported.

In the linotype machine, matrices are brought down from the magazine

by touching the corresponding letters on the type indicator until

they are arranged so as to form the line; a lever then carries them

sideways into position, so as to allow the molten metal to flow into

the mould and cast the line. Another lever then raises the matrices,

which are carried into the magazine again, the slab of metal with the

cast line upon it falling into a receptacle. Here, again, danger of

lead fume is hardly in question. As the matrices drop down from the

magazine, particles of lead which they have gathered when in contact

with the metal are detached, and are visible on every linotype machine

at this point. The brass cover of the magazine, if not frequently

cleaned, soon becomes coated with fine dust. Although lead fume may

not be given off, it is none the less necessary to remove the products

of combustion from the heating apparatus, in order to prevent constant

vitiation of air and to reduce the temperature in the neighbourhood of

the machines. Monotype machines give off much heat. Exhaust ventilation

by hoods reaching well over the pots, and branch ducts entering the

main duct in connection with a fan tangentially, can alone accomplish

this satisfactorily. Hoods and ducts leading merely into a shaft

running up the side of the building fail to prevent condensation of

the water vapour, which in consequence trickles back. Wherever a

well-thought-out system of exhaust ventilation has been installed,

reduction in temperature and comfort to the operatives has been

secured. Temperatures above 65° F. must incommode a linotype operator.

[Illustration: FIG. 11.--EXHAUST VENTILATION ON THE PATENT “PENTARCOMB”

PRINCIPLE APPLIED TO METAL MELTING-POTS, ETC., IN PRINTING FOUNDRY, AS

INSTALLED BY THE ZEPHYR VENTILATING COMPANY, BRISTOL.

P, Patent “pentarcomb” for equalizing exhaust; D, main and branch

ducts; U, upcast from fan; F, fan; H, hoods over melting-pots and dross

drums; S, stereo metal melting-pots; B, boxes or drums for dross.

The illustration shows exhaust ventilation applied to the melting

and stereo pots and dross drums in a letterpress printing foundry.

The draught over each pot is equalized at the point where the branch

ducts join the main duct by insertion of a patent “pentarcomb” grid,

which breaks up the columns of air into numerous smaller channels by

specially curved metal plates so as to minimize friction. The ducts are

graduated, and the exhaust is provided by a volume fan.]

In the foundry the recasting of old used type, etc., is effected, and

periodically scraps and sweepings are melted down. These melting-pots

should have telescopic hoods so balanced that they can readily be

lowered, so as to enclose the bath of molten metal and allow the

fume to be drawn by the fan into a duct of such width as to offer no

obstacle to escape. A duct too narrow to deal with the great expansion

the heated air undergoes is a defect very frequently found. A principal

source of danger is the skimming of the melting-pot for sweepings,

etc., and deposit of the large amount of dross by the side of the pot.

Receptacles for the dross in connection with the exhaust system are

imperatively needed.

Exhaust, where practicable, over the often large melting-pot for

stereotype casting is desirable, in order to secure a reasonable

temperature. Here there is the danger of splashing of molten metal,

which is subsequently trodden underfoot.

_Compositors’ Work._--The letters are distributed in the small

compartments of the type cases. From attrition dust may lie thick in

the compartments, and when at work there is always tendency for small

quantities of this dust to be dispersed. While this is the principal

source of poisoning, inasmuch as dust containing lead must adhere to

the fingers, lead may thus enter the system with food or when smoking.

It is quite as easy, also, to believe that lead poisoning may result

from solvent action of the blood and tissue fluids on small spicules of

lead type which penetrate the skin as to credit the well-substantiated

cases of plumbism ensuing on retention of bullets or shot in the body.

Compositors sometimes contract the habit of holding type between their

teeth.

The old dangerous method of blowing out the dust on the staircase by

means of a bellows should before long be entirely supplanted by use

of suction bellows or use of printers’ case dust-extractors. In the

Clements apparatus the cases are placed on a shelf, which is made to

oscillate; air is forced into the compartments from numerous jets, so

as to raise the dust, which is removed by suction and collected. The

cases are thus cleaned with great saving of time in the composing-room

itself, and without contamination of the general atmosphere by dust.

The dust removed from a composing box by a vacuum cleaner was found in

the Government laboratory to contain 9·8 per cent. of metallic lead,

and that collected from the top of the magazine of a linotype machine

8·18 per cent.

Regulations issued in 1911 in Austria require, among other things--(1)

Melting-pots, and, so far as is practicable, linotype pots also, to be

provided with hoods and ducts to carry the fumes to the outside air or

into a chimney; (2) the type cases to fit either close on to the floor

or with a sufficient space below the lowest drawer to enable the floor

underneath to be easily cleaned; (3) the interior of all compositors’

boxes to be cleaned at least once every three months--if possible,

by means of a vacuum suction apparatus; and (4) quarterly periodical

medical examination to be made of persons employed in casting,

stereotyping, linotyping, assorting type, and composing.

Sommerfeld[12] believes that in Berlin 1·07 per cent. of the

compositors suffer from lead poisoning every year, and that 2·5 per

cent. of all the diseases they suffer from are due to lead. Among 3,641

printers applying for sick relief, Silberstein[13] found 65 suffering

from lead poisoning (1·7 per cent.). Where, however, diagnosis of

lead poisoning is based upon examination of the blood, as in Leipzig,

the amount of compensation paid by the Sickness Insurance Society has

diminished considerably. Thus, of 207 compositors who were either sent

by medical men as cases of, or went themselves suspecting that they

were suffering from, lead poisoning, only 17 (8·2 per cent.) showed

basophilia to such degree as to warrant the diagnosis. The proportion,

on the other hand, among letter founders and electrotypers was 28·6 per

cent.

Printers suffer extensively from phthisis, their comparative mortality

from this cause as compared with the figure for all occupied males

being 290 : 175[14]. This high mortality is probably due mainly to the

vitiation of the atmosphere, and reluctance, on account of extreme

sensitiveness to draughts, to admit fresh air. This closing of windows

by persons employed should be an additional reason for checking the

vitiation from Bunsen burners in connection with linotype and monotype

machines by the only practicable means of preventing perceptible

draught--namely, exhaust ventilation.

=File-Cutting[15].=--The steel file to be cut is placed on a stone

block in the centre of which is inserted a smaller steel block, called

a “stiddy.” The worker holds in his right hand a hammer, weighing

sometimes 7 or 8 pounds, and in his left, closely gripped, a chisel.

Each tooth in the file--and there may be as many as 3,800 teeth to be

cut--is the result of a blow on the chisel, and we have counted as many

as 120 blows with a 7-pound and 200 with a 4-pound hammer per minute.

To offer resistance to the blow and yet prevent a recoil, the file (in

the case of the finer kinds) is placed on a lead bed--that is, a thin

strip of metallic lead. With attrition from repeated impact the lead

bed becomes worn away in the course of a few days, and part of what is

so worn away necessarily takes the form of lead in fine particulate

state.

_Dangers._--Absorption of lead follows from the dust generated by each

blow, from brushing the dust off the cut file, and from licking the

finger and thumb holding the chisel. Other conditions predisposing

to plumbism before the present regulations came into force, and not

altogether without effect still, were--too close proximity of one stock

to another, defective ventilation of the (frequently) small shed in

which the work was done, overcrowding, accumulation of dust on the

benches, uneven floors, inadequate washing facilities, and, apparently,

lack of appreciation of the danger.

The remarkable feature of plumbism in this industry is the long

duration of employment before pronounced symptoms manifest themselves

(see p. 51). The insidious onset is, however, accompanied by an

undermining of the constitution, showing itself eventually in atrophy

of the muscles, especially of the thenar and hypothenar eminences

of the hand, and of the lumbricals and interosseous muscles of the

fingers, the result of continual gripping of the hammer and chisel,

chronic interstitial nephritis, with its associated arterio-sclerotic

changes, and heavy incidence of phthisis.

Provision of locally applied exhaust ventilation has never been

suggested for this industry, owing to absence of power to drive a fan

in the small workshops, and because no lead dust is seen to be given

off. Diminution in the number of cases is due to the fact that machine

file-cutting (with zinc as the bed) has been substituted for hand

file-cutting for coarse files. In hand cutting, in some instances, beds

of pewter, or of alloys with comparatively small proportion of lead,

have replaced the use of lead beds. The remedial measures prescribed in

the regulations have also played a part.

At the time the regulations came into force, in 1903, there were about

708 file-cutting shops in the United Kingdom, of which 517 were in

Sheffield. Immediately after they came into force 126 certificates of

exemption were granted for use of beds containing less than 5 per cent.

of lead, and every year fresh applications are received[16]. There does

appear, however, to be difficulty in securing beds which conform to the

standards laid down. Thus, in the four years 1907-1910, of 23 samples

submitted as containing less than 5 per cent., 16 were in excess.

The number of reported cases of poisoning in the five years 1900-1904

was 151, and 51 in the five later years 1905-1909. The attack rate is

about 10 per 1,000, but, although this may be low compared with other

trades, the much greater severity of the attacks has to be borne in

mind.

=File-Hardening.=--The process consists in keeping the files in a bath

of molten lead at high temperature, covered with charcoal. The file is

removed when red-hot, straightened if necessary, and plunged into a

solution of brine.

_Dangers and Prevention._--Poisoning is attributable to fume given

off by the molten lead (a temperature of 850° C. was recorded by S.

R. Bennett--see p. 201), risk of which can only be met by efficient

hooding and exhaust unless an alternative method of hardening is

adopted, dispensing with the lead bath--_e.g._, by exposure to heat on

a hearth, in a gas furnace, or by other means. In this small industry

in and around Sheffield three cases were reported within a year,

each involving partial or complete paralysis of the extensors of the

forearm. Of ten men employed at the work, three showed presence of

a blue line, three were cachectic, and one had weakness of the arms

and wrists. In two of the three factories attempts had been made

unsuccessfully to carry the fumes away by a hood and duct[17].

Hardening of forks and similar articles in the same manner has also

given rise to poisoning.

We are informed that methods of hardening and tempering drills, tools,

etc., by the use of fused metallic salts, are being adopted in some

works. By mixing together two or more salts in definite proportions,

suitable fusing-points can in all cases be produced. These baths can

be raised to any desired melting-point to suit the requirement of

different steels. For example, sodium nitrate and potassium nitrate in

certain proportions give melting-points from 220° to 340° C., and can

be used for tempering baths up to 600° C. For tempering above 600° C.

mixtures of sodium chloride and potassium chloride can be used, whilst

for hardening, sodium chloride or barium chloride give adequate ranges

of temperature. Similarly, mixtures of sodium sulphate (melting-point,

890° C.) and lithium sulphate (860° C.) can be made to give any

melting-point from 605° to 860° C.

=Tinning of Metals[18].=--Cheap hollow-ware vessels such as kettles

and frying-pans are often coated with a mixture of (usually) half lead

and half tin by dipping them into a bath of the molten metal, after

cleaning in hydrochloric acid.

_Danger and Prevention._--Duckering has shown (see p. 203) that fumes

of chloride of lead are given off which are especially noticeable

when the dipped article is removed to a stand to have the superfluous

metal wiped from it with tow while still in a molten state. Detailed

reference is made on p. 204 to the nature of the fume given off and the

amount of lead present in the atmosphere breathed and inhaled daily by

the worker.

The danger from fumes can be in great measure removed, both from the

bath and from the wiping stand, by locally applied exhaust ventilation,

which may be secured by utilization of the draught from the fire under

each melting-pot, or by a hood and duct carried vertically through

the roof if arranged as described on p. 209. Danger from dust arises

also from the skimmings, if not deposited in a receptacle within the

hood, from dust and débris on the floor, and possibly from traces of

metallic lead and lead chloride attached to particles of tow floating

in the air. Risk of lead absorption is less in later processes, such

as affixing the spout and handle (mounting), and hammering or denting.

Occasionally roughnesses are removed by rubbing the coating with emery

paper.

_Harness Furniture._--Hames, buckles, bits, etc., are usually coated

with nickel or copper, more rarely with silver. The process is in the

nature of soldering, and the steel, prepared in the same way as has

been described for hollow-ware, has a mixture of two parts tin and

one part lead poured over it on a hearth. The strip of thin nickel

sheeting is passed through a similar mixture, and is wiped with

tow--the operation to which such poisoning as occurs in this industry

is mainly due, in consequence of the difficulty of efficiently removing

the vapour of lead chloride from the molten metal upon the long strip

of nickel. Subsequently the prepared steel article and the strip of

nickel or copper are made to unite under pressure of a soldering-iron.

In silver plating danger from fume is slightly less, as the steel

portion (for example, the hame) only is tinned. In the final operation

of polishing on a mop danger arises from dust, unless locally applied

exhaust is provided.

_Iron Drums and Kegs._--Use of a tinning mixture of lead and tin in

this industry is obviously in the nature of soldering. The body of

the drum is made either of black sheet-iron or of terne (lead-coated)

sheet. In order to unite the seam and to fix the bottom sheet, the drum

is made to stand in a shallow bath and laid on its side. The danger

from lead chloride vapour is considerable, and the method of prevention

is precisely of the kind described above.

Similar coating of articles first cleaned in hydrochloric acid is

met with, as, for example, of the component parts of radiators of

motor-cars, of steel bars, and of wire. Incidence of poisoning has not

occurred to an extent to make necessary more than the application of

locally-applied exhaust to remove the fumes.

_Manufacture of Terne Plates._--The manufacture of lead-coated sheets

for roofing purposes is carried on in a few works in South Wales along

with the manufacture of tin plates. Lead poisoning in the industry

is practically unknown. We can only recollect occurrence of one

case, despite the fact that the mixture contains from 65 to 95 per

cent. of lead. For cleaning the plates prior to passing them through

the concentrated zinc chloride flux into the molten mixture, dilute

sulphuric acid is used, and not hydrochloric acid. As to the remarkably

different results on health of the two processes, Duckering concludes:

“The absence of lead poisoning among terne-plate workers and tinners

would appear to be explained by--(1) The use of cleaning agents and

a flux of such a nature, and in such a way, as to involve a minimum

contact with the tinning metals, and under such conditions as to

inhibit extensive interaction between them, and also under such

conditions as to inhibit production of fume or vapours, even if

any interaction occurs; (2) use of a scientifically prepared flux

containing no uncombined acid or excess of water in such a way as to

prevent introduction of these substances, or of ferrous compounds

coming into intimate contact with the tinning metal; (3) so conducting

the operation of tinning that any chlorides possibly adhering to the

plates are removed before the plate reappears in the open air, under

conditions preventing them from appearing in the air as vapour, but

it is very doubtful whether any chlorides could adhere to the plates;

and (4) absence of any manual work on the plates before the metallic

coating is set and hard. On the other hand, the existence of widespread

lead poisoning in tinning of hollow-ware is explained by--(1) Use of

cleaning agents and flux in such a way as to bring these materials into

intimate contact with the tinning metals under conditions eminently

favourable to chemical interaction and vaporization of resultant

compounds; (2) use of an unscientifically prepared flux containing

a large excess of water and much free acid; (3) so conducting the

operations as to favour the escape into the atmosphere of vapours of

soluble lead compounds, such as lead chloride, and of metallic lead and

soluble lead compounds, carried mechanically by fibres of tow during

processes subsequent to tinning, as in wiping; and (4)--a minor point

not to be lost sight of--possibility of contamination of the hands by

soluble lead compounds, due to manipulating the material with which the

articles are wiped.

“It should be added that while use of a scientifically prepared

flux [(2) above] in hollow-ware tinning would no doubt lessen the

possibility of the production of fumes, it is not to be anticipated

(unless a flux containing no chlorides were used) that this would do

away with lead poisoning. In other words, the method of use is, as

indicated above, a far more important factor.”

In the ten years 1900-1909 the number of reported cases in tinning

hollow-ware was 93 among about 200 persons employed, in harness

furniture 23 among about 150 persons employed, and in iron drums and

kegs 47 among about 250 persons employed.

=Plumbing and Soldering.=--The figures included in the table on p.

47 have reference only to these processes as carried on in factory

premises. House plumbers, when reported, are included with house

painters. The figures are made up of two classes--(1) Those handling

white and red lead paste, and (2) those engaged in soldering and lead

burning. The number of cases reported in the ten years 1900-1909 was,

in the first class 122, and in the second 95.

Any worker using red lead as a jointing paste who is not a house

plumber or a coach or ship builder is included under the first heading,

as, for example, electricians, persons engaged in mechanics’ workshops,

lead-light making where red lead cement is brushed between the lead

lines and the glass to render them water-tight, and such occupations

as placing strips of canvas coated with red lead between sheets of

iron work before riveting, so as to afford protection against rust. In

several reports there is reference to the dust created in the breaking

up of old joints with aid of hammer and chisel before proceeding to

recaulk them.

Dust in making up the paste is the principal source of danger. This is

crudely done, and unless large quantities of paste are made exhaust

ventilation is never provided, in view of the intermittency of the

work. The wearing of a respirator should be possible, but it would

be unsafe to recommend that as a sufficient means of prevention.

Installation, whenever possible, of localized exhaust ventilation at

the mixing bench is most desirable. Personal cleanliness is important,

as the hands become ingrained with the paste.

The heading “Soldering” includes in the main (_a_) the soldering of

tins of all descriptions, bicycle lamps, etc., with a stick of solder,

either held in the hand or lying on the bench, which is touched by the

hot soldering-iron, the surface to be soldered having previously been

cleaned with “killed spirit”--_i.e._, zinc chloride flux; and (_b_)

lead burning, by means of a hydrogen or oxy-hydrogen blowpipe flame, of

lead-lined boxes, vats in sulphuric acid and other chemical works. Some

cases are included which occurred in the manufacture of solder itself.

Green wood is held at the bottom of the pot of molten metal, and the

gases distilled from the wood pass upwards through the metal and escape

at the surface, carrying small quantities of lead into the atmosphere

of the workroom.

_Dangers and Prevention._--It can be confidently said of soldering

that, bearing in mind the very large number of persons employed, the

number of cases reported is remarkably small, and it is difficult

to assert generally, as can easily be asserted of tinning, that

inhalation of soldering fumes must necessarily set up lead poisoning.

Moreover, examination of persons employed in soldering for signs of

lead absorption is almost always negative, a blue line on the gums even

being rarely visible.

On the other hand, the process of soldering is so analogous to that of

tinning that such poisoning as occurs is probably due to inhalation

by susceptible persons of lead chloride fumes. And this is borne out

by the results of analysis in the Government laboratory of a sample

of deposit collected from a duct where exhaust ventilation had been

applied to take away the fumes.

The material was a black mass, obviously containing a large

proportion of carbon.

On completely extracting with water, the solution was found to show

an acidity equal to 0·20 per cent. of hydrochloric acid calculated

on the original sample, and in this solution the following metallic

substances were present--viz.:

Percentage on

Original Substance.

Zinc, calculated as zinc chloride 19·53

Copper, calculated as copper chloride 1·77

Lead, calculated as lead chloride 0·19

Tin and arsenic were both absent, and the chlorine present closely

corresponded with the proportion of chloride shown above.

The portion of the substance which was insoluble in water was found to

contain the following metallic substances:

Percentage on

Original Substance.

Tin, calculated as tin oxide 6·09

Lead, calculated as lead oxide 1·33

Copper, calculated as copper oxide 0·57

Zinc, calculated as zinc oxide 0·20

This portion of the sample was also free from arsenic.

We believe that where soldering is done by several persons in a

workroom, inhalation of the fumes is prejudicial to health, and that

the usual methods of localized ventilation are desirable. Where this

has been done the result has been in every way satisfactory.

In lead burning the heat from the blowpipe flame is sufficient, if kept

long enough in contact with the lead sheet, to cause volatilization

of the metal, and, as the worker’s face must necessarily be close to

the flame, inhalation of fume is inevitable. Such work, however, has

often, unfortunately, to be carried on in confined spaces where exhaust

ventilation cannot be applied.

=Brass[19].=--The malady the brass caster has suffered from in the past

is _par excellence_ brassfounders’ ague. Lead, however, is introduced

(rarely exceeding 10 per cent.) for the purpose of softening the alloy

of copper and zinc. Of 77 cases of lead poisoning in the ten years

1900-1909 included under the heading “Brass,” 38 were polishers, 28

casters and others, and 11 chandelier fitters. Cases occur among the

casters probably from inhalation of the fumes in pouring, and among the

polishers from inhalation of the small proportion of lead in the dust

given off in the absence of adequate exhaust. In a factory where there

were two emery wheels, one with a hood and fan to carry the dust away,

while the other remained unprotected, the worker at the unguarded wheel

suffered from lead poisoning. In filing and dressing the article is

held in a clamp with leaden claws, which gradually become worn away,

just as does the lead bed used by the file-cutter. This may account for

the poisoning reported among filers and dressers.

A sample of dust taken from under a calico mop for brass polishing was

found in the Government laboratory to contain 2·1 per cent. of lead.

The joints of chandelier fittings are sealed with a white lead paste.

Instead of always testing the completeness of the seal by means of an

air pump and pressure gauge, the fitter frequently tests it by applying

his lips to the unsealed end and blowing through the pipe. All the

cases among chandelier fitters are caused in this way--perhaps the

clearest instance of poisoning by absorption through the alimentary

canal, as distinguished from absorption through the lungs, that can be

cited. While use of an air pump and immersion of the joint in water or

pressure gauge only is an entire protection, and should be provided

wherever this work is done, constant supervision as to its use is

called for. The sealing of the joint can be done with a material known

as “caulkite,” containing neither white nor red lead.

For references, see end of Chapter XVII.

CHAPTER XVI

DESCRIPTION OF PROCESSES--_Continued_

=Manufacture of White Lead[20].=--The usual method in this country is

that known as the “Dutch process,” although the German chamber process,

precipitation processes, and others, are all practised.

_Dutch Process._--A layer of spent tan is placed on the floor of the

stack (a chamber with walls of brick some 25 feet high, and a vertical

opening from top to base through which the men enter), upon which are

arranged earthenware pots partially filled with dilute acetic acid.

Strips of lead are then placed on small square “cockney” pots, or more

rarely in the form of folded grids, inside deep, long “castle” pots,

and the whole covered with boards, resting on special “bearer pots”

containing dilute acetic acid. Ten to fifteen of such layers (blue

beds) one on the top of the other are built into the stacks to a height

of some 20 feet. When completed, the stacks remain for 80 to 100 days

before being emptied. During this period the temperature rises to 75°

to 80° C., considerable evolution of carbonic acid gas takes place, and

the lead is converted first into acetate and subsequently the white

basic carbonate. The layers (white beds) are uncovered and the corroded

strips (corrosions) collected by hand. They are placed in trays and

carried to heavy steel rollers by means of which and subsequent raking

in wash becks the carbonate is detached from the uncorroded central

core of blue lead. In many factories corrosions are now conveyed

from the stacks to the wash becks or rollers by travelling cranes.

The recovered blue lead is removed in a wet state to be remelted and

recast. The corrosions, after passing through the rollers and wash

becks, are shovelled on to a picking-board and transferred gradually

to the grindstones. From the stones the ground pulp passes to the

settling becks through several gratings of fine copper mesh. In the

form of pulp the material is ladled by hand into bowls for conveyance

to the drying stoves. When dry, the contents of the bowl are emptied

into barrels and headed, or into hoppers, from whence the material is

conveyed to be packed either by hand or automatically by mechanical

packers, or to be converted into paint.

_Dangers and Prevention._--In casting the strips, risk does not arise

from lead fume, as the temperature at which this is effected (350°

C.) is too low for appreciable fume to be given off. Danger here is

from skimmings and deposit of them on the floor or into a receptacle

unprovided with exhaust draught. Pots in which remelting of the

uncorroded cores (returns) is done should be provided with hoods and

exhaust, because of the dust given off in stirring and skimming and the

spurting which occurs as they are thrown in wet. In making the blue

beds, dust arises from particles of white lead adhering to the pots

and in the tan bark. Pots, on removal from the white beds, should have

all white lead inside them removed by washing in a tank. Screening of

the bark should be dispensed with. Emptying the white beds accounts,

perhaps, for the largest number of cases, owing to the impossibility,

in the present state of knowledge, of dealing with the dust by means

of exhaust ventilation, or quite adequately by watering or wearing of

respirators. Watering by means of a hosepipe with rose attached is,

however, the main safeguard. Substitution of the square cockney pots

for the long castle pot is also of moment, as the flat plates of lead

form a denser and more porcellanous corrosion than that of the grids in

the castle pots. Moreover, in stripping the beds the flat corrosions

can be lifted into trays without creating dust, whereas to dislodge the

contents of the castle pots may require a sharp tap, and the unglazed

portion of the interior surface of the latter retains some carbonate

when moistened. Watering requires to be thorough and done with care,

or else the softer material of the corrosion may be washed into the

tan. No less important is it to water the layers of tan, and at a time

while they are yet warm and slightly damp, otherwise the tan becomes so

dry that the water runs through, and does not adequately prevent dust

formation on its removal. A requirement of the special rules is that

the trays for collecting the corrosions shall not stand directly upon

the beds. When corrosions contain an undue proportion of lead acetate,

they are termed technically “floury,” and much dust may arise from

them on watering unless this be done with a very fine rose.

Dust at the rollers and wash becks is usually checked by preliminary

immersion of the tray of corrosions in a trough of water, but the extra

weight of the water causes this sometimes, in the absence of mechanical

arrangements for immersion, to be done perfunctorily. Where there

are rollers, the tray is inserted in a small opening above them, the

contents saturated by a spray, and then tipped over. This method also

may fail to control the dust, as, unless the men engaged in washing the

corrosions in the wash beck keep the mass tipped in from piling up in

a heap, the contents of the trays are discharged on to the heap, and

not into water. In some factories exhaust ventilation at the rollers or

wash becks has been necessary.

During subsequent wet processes of grinding danger is mainly from

splashing. From the settling tanks the white lead is pumped into

filter presses, and the resulting cake is dried. Here the considerable

risk from splashing is again almost unavoidable. Concrete floors are

necessary. Emptying the stoves involves much handling, with inevitable

creation of dust, especially when the bowls are withdrawn from the

racks. Risk has been greatly lessened by reducing the height of

the shelves to 10 feet and prohibiting the piling of one bowl upon

another. Mechanical drying stoves into which men need not enter either

for filling or drawing are now commonly met with. Of these there

are various types--(1) Horses similar to those common in laundries,

which can be withdrawn on rails; (2) small chambers built up one upon

another somewhat in the form of gas retorts in a gasworks, heated by

steam jackets and coils, each chamber containing only two or three

cakes of white lead pulp, the cakes themselves being removed by a

mechanical process from the press into the drying chambers; (3) bogies

carrying the white lead in bowls on racks made to pass through the

tunnel-like stove; (4) drying machines--_i.e._, closed cylinders fitted

with a series of platforms so arranged that they may be charged with

white lead on one side, and so fixed as to be turned round by means

of mechanical appliances. When dry, the material is discharged into

a chute by a series of scrapers into a small enclosed compartment,

holding the barrel to be filled. With the drying machine, however,

there is considerable risk of dust leakage, especially when the doors

are opened. In packing by hand, safety depends on efficient exhaust

ventilation when the contents are tipped into the barrel, but a danger

constantly present is that, to get through the work quickly, the bowls

may be withdrawn from the influence of the exhaust before the last

traces of dust have been removed from the bowl. Mechanical packing, by

means of a large bladed screw forcing the white lead into the barrel,

which as it becomes filled is lowered automatically, is everywhere

desirable. An essential condition of this method is that a dust-proof

collar should connect the automatic packer with the barrel. Some dust

almost inevitably escapes, and a hood and exhaust should be provided,

however perfectly the machine is said to act.

Much of the white lead is converted into paint on the premises,

being ground in oil either in pug mills, Torrance mills, or under

edge-runners. A negative pressure must be maintained inside the casing,

which must enclose the stones. Here the conditions are precisely those

described under the manufacture of paints and colours. In some white

lead works conversion into paint is done without the dangerous process

of stove drying, either by drying under a vacuum or by mixing the white

lead directly with oil. In the process of grinding the oil incorporates

itself with the white lead, and the water is forced out, running away

in a clear stream.

_Chamber Process._--In this method, almost universally used in Germany,

and adopted in at least one large white lead works in this country,

a chamber arranged with numerous sets of parallel bars on which the

thin strips of lead are set saddle-wise takes the place of the stack

in the Dutch process. Carbonic acid gas and acetic acid vapour act

on and corrode the strips. In a period of from eight to ten weeks

the corrosions mostly fall to the ground. Such of the strips as do

not fall have to be lifted off the bars, having been previously well

saturated with water from a hosepipe, and are dropped on to the floor

of the chamber. We are not satisfied that working in the dark, confined

chamber by artificial light is less dangerous than working on the

stacks. Chamber-made lead undergoes practically the same subsequent

processes as have been described.

_Precipitation Processes._--These also dispense with stacks and the

consequent risks attending work on the blue and white beds, but they

substitute another--namely, use of oxide of lead (litharge or the

suboxide) as the initial product to be carbonated, with the inevitable

danger, in the absence of mechanical contrivances entirely closed in,

of shovelling dusty material. In many of these methods, however,

mechanical arrangements obviate hand labour or contact with dust in all

but the first process.

The Brimsdown process[21], for instance, is automatic and free from

dust, except in the initial stage of preparation of litharge in

cupellation furnaces. The great risk from the disintegration of this

material (see p. 250) by turning it out on the floors is obviated

by allowing disintegration to take place in the pots (which must

not, therefore, be completely filled), and tipping these when cooled

directly into a breaker under powerful exhaust draught. From the bin

into which it falls the material is conveyed by dust-proof elevators

to (_a_) screens and packing arrangements when the object is flaked

litharge, or (_b_), in the case of the bulk of the material for

manufacture of white lead, by enclosed conveyors to reducers and mixing

mills, where reduction and hydration take place. It is then charged

automatically into weak solution of acetic acid, and by agitation with

carbonic acid gas converted into basic carbonate of lead. From the

carbonators pumps force it into filter presses, where the acetate is

drained off and washed out by pure water. The cakes of white lead are

fed into mixing machines and pugged with linseed-oil until the water

has been entirely removed, and finally passed through the roller mills

to be packed in casks.

Dry white lead is made by feeding a metal travelling lattice with pulp

white lead inside a drying chamber entirely closed in. When dry, the

white lead is automatically brushed off, elevated, and automatically

packed in a chamber under efficient exhaust draught. In this part of

the process, therefore, risk to the workers is very small.

The stringent Special Rules for the White Lead Industry show

what other precautions, in addition to exhaust ventilation, are

necessary--especially personal cleanliness. The effect of one other

factor--casual labour--however, must be referred to. The condition at

the present time is very different from that which existed twelve years

ago. From one factory in 1899, depending much on casual labour, 111

cases were reported, and from another 72. In an inquiry made by one of

us in 1898, information was obtained of the actual number employed on

any one date, and of the total number passing through the factories in

a year.

Among the firms with regular employment at that time, the incidence of

lead poisoning was 60 per 1,000 on the average number employed, and in

those with casual employment 390 per 1,000. Work in lead had secured a

bad name, and no one who could get employment elsewhere would take to

it. Consequently, the class of men applying for work was a low one--men

discharged from other employment and those unfitted for skilled labour.

Not a few were addicted to alcohol. The work was unskilled, and had the

additional advantage to men of that class that much of it was piece

work, paid at a good rate, which could be finished as a rule by three

o’clock in the afternoon.

Diminution in the number of cases from 399 in 1899 to 34 in 1910 has

been brought about mainly by--(1) Improved structural conditions;

(2) adoption of mechanical means (cranes, rails, hoists, etc.) for

conveyance of material in substitution for hand carrying; (3) exhaust

ventilation, where dust arises as in packing and paint-mixing; (4)

periodical medical examination; (5) diminution in height of the stoves

or adoption of mechanical drying stoves; (6) conversion of white lead

into paint by means of direct mixture with oil while in the pulp

stage; and (7) substitution of small, square, glazed pots--cockney

pots--requiring the lead strips to be placed on them, for the deep

castle pots into which the lead grids are folded in the white beds.

Prohibition of female employment in the dangerous processes was made

prior to the Special Rules of 1899. Their greater susceptibility as

compared with men, the special effect of lead on the uterine functions,

and the unsuitability of much of the work for women, fully justified

the step recommended by the White Lead Committee in 1898.

=Earthenware and China[22].=--The industry includes the manufacture of

earthenware, china, tiles, majolica ware, Rockingham ware (teapots),

sanitary ware, china furniture, and electrical fittings, and any other

articles made from clay; but of the total 6,865 persons employed in

lead processes in the whole of the United Kingdom in 1907, 5,834

are included in the manufacture of the first three. And even in the

manufacture of earthenware, china, and tiles, the poisoning which

occurs is not distributed evenly over the whole of the factories.

These number 550, and, taking the period 1904-1908, 5 potteries were

responsible for 75 cases, 17 for 119, and 151 for 323, leaving 377

factories out of the 550 from which no case was reported. Incidence

seems to depend more on the scale and rapidity of the output of cups,

saucers, plates, and tiles, in everyday use, than on anything else.

The number of reported cases year by year from 1900 to 1909 has been as

follows:

ALL LEAD-WORKERS IN PLACES UNDER EARTHENWARE AND CHINA SPECIAL RULES.

WHOLE OF UNITED KINGDOM (INCLUDING NORTH STAFFORD).

NUMBER OF PERSONS EMPLOYED.

+-------+----+------+------+-----+-----+------+-----++-------+-------+

| | | | | | | | || | |

| | | | | | |China,| || | |

| | | | | | |Furni-| || | |

| | | | | | | ture | || | |

| | | | | | Jet | and | || | |

| | | | | | and | Elec-| || | |

| | |Earth-| | Ma- |Rock-|trical| || |Totals,|

| |Chi-| en- | |joli-| ing-| Fit- |Sani-|| | M. and|

| | na.|ware. |Tiles.| ca. | ham.|tings.|tary.||Totals.| F. |

+-------+----+------+------+-----+-----+------+-----++-------+-------+

|1904 M.| 536| 2,751| 557 | 100 | 216 | 44 | 190 ||4,394 }| 6,694 |

| F.| 238| 1,122| 562 | 110 | 71 | 158 | 39 ||2,300 }| |

|1907 M.| 625| 2,835| 474 | 96 | 171 | 66 | 237 ||4,504 }| 6,865 |

| F.| 302| 1,111| 487 | 170 | 70 | 179 | 42 ||2,361 }| |

+-------+----+------+------+-----+-----+------+-----++-------+-------+

NUMBER OF CASES OF LEAD POISONING.

+----------+------+------+------+------+------+------+------+------+

| | | per | | per | | per | | per |

| |Cases.|1,000.|Cases.|1,000.|Cases.|1,000.|Cases.|1,000.|

+----------+------+------+------+------+------+------+------+------+

|1899 M.| 13 | 24 | 106 | 39 | 7 | 13 | 2 | 20 |

| F.| 8 | 34 | 83 | 74 | 21 | 37 | 4 | 36 |

|1900 M.| 11 | 21 | 62 | 23 | 12 | 22 | 3 | 30 |

| F.| 10 | 42 | 67 | 60 | 15 | 27 | 2 | 18 |

|1901 M.| 7 | 13 | 37 | 13 | 9 | 16 | -- | -- |

| F.| 2 | 8 | 28 | 25 | 7 | 12 | 2 | 18 |

|1902[A] M.| 3 | 6 | 30 | 11 | 6 | 11 | -- | -- |

| F.| 2 | 8 | 33 | 29 | 5 | 9 | 2 | 18 |

|1903 M.| 1 | 2 | 29 | 11 | 8 | 14 | 1 | 10 |

| F.| 6 | 25 | 32 | 29 | 9 | 16 | 6 | 55 |

|1904[B] M.| 2 | 4 | 31 | 11 | 6 | 11 | -- | -- |

| F.| 1 | 4 | 41 | 37 | 19 | 34 | 1 | 9 |

|1905 M.| 4 | 8 | 25 | 9 | 4 | 7 | -- | -- |

| F.| 3 | 13 | 23 | 20 | 14 | 25 | 4 | 36 |

|1906 M.| 5 | 8 | 34 | 12 | 7 | 15 | -- | -- |

| F.| 2 | 7 | 41 | 37 | 10 | 21 | 3 | 18 |

|1907 M.| 6 | 10 | 38 | 13 | 4 | 8 | -- | -- |

| F.| 7 | 23 | 33 | 30 | 6 | 12 | 1 | 6 |

|1908 M.| 4 | 6 | 45 | 16 | 3 | 6 | -- | -- |

| F.| 1 | 3 | 42 | 38 | 8 | 16 | 1 | 6 |

|1909 M.| 2 | 3 | 22 | 8 | 4 | 8 | -- | -- |

| F.| 1 | 3 | 17 | 15 | 7 | 14 | -- | -- |

+----------+------+------+------+------+------+------+------+------+

+----------+------+------+------+------+------+------+

| | | per | | per | | per |

| |Cases.|1,000.|Cases.|1,000.|Cases.|1,000.|

+----------+------+------+------+------+------+------+

|1899 M.| -- | -- | -- | -- | -- | -- |

| F.| -- | -- | 5 | 32 | -- | -- |

|1900 M.| 5 | 23 | 1 | 23 | 1 | 5 |

| F.| -- | -- | 11 | 70 | -- | -- |

|1901 M.| 3 | 14 | 1 | 23 | -- | -- |

| F.| 1 | 14 | 9 | 57 | -- | -- |

|1902[A] M.| -- | -- | -- | -- | 1 | 5 |

| F.| 1 | 14 | 4 | 25 | -- | -- |

|1903 M.| 3 | 14 | -- | -- | 1 | 5 |

| F.| -- | -- | 1 | 6 | -- | -- |

|1904[B] M.| -- | -- | -- | -- | -- | -- |

| F.| 1 | 14 | 4 | 25 | -- | -- |

|1905 M.| -- | -- | 2 | 45 | 1 | 5 |

| F.| 2 | 28 | 2 | 13 | -- | -- |

|1906 M.| -- | -- | -- | -- | 1 | 4 |

| F.| -- | -- | 3 | 17 | 1 | 24 |

|1907 M.| 1 | 6 | -- | -- | 3 | 13 |

| F.| -- | -- | 3 | 17 | 1 | 24 |

|1908 M.| 1 | 6 | 1 | 15 | 2 | 8 |

| F.| -- | -- | 8 | 45 | 1 | 24 |

|1909 M.| -- | -- | -- | -- | -- | -- |

| F.| 2 | 29 | 2 | 11 | 1 | 24 |

+----------+------+------+------+------+------+------+

+----------++------+------+------+------+

| || |Attack| Total|Attack|

| || | Rate |Cases,| Rate |

| || Total| per | M. & | per |

| ||Cases.|1,000.| F. |1,000.|

+----------++------+------+------+------+

|1899 M.|| 128 | 29} | 249 | 37 |

| F.|| 121 | 53} | | |

|1900 M.|| 95 | 22 }| 200 | 30 |

| F.|| 105 | 46 }| | |

|1901 M.|| 57 | 13} | 106 | 16 |

| F.|| 49 | 21} | | |

|1902[A] M.|| 40 | 9 }| 87 | 13 |

| F.|| 47 | 20 }| | |

|1903 M.|| 43 | 10} | 97 | 14 |

| F.|| 54 | 23} | | |

|1904[B] M.|| 39 | 9 }| 106 | 16 |

| F.|| 67 | 29 }| | |

|1905 M.|| 36 | 8} | 84 | 13 |

| F.|| 48 | 21} | | |

|1906 M.|| 47 | 10 }| 107 | 16 |

| F.|| 60 | 25 }| | |

|1907 M.|| 52 | 12} | 103 | 15 |

| F.|| 51 | 22} | | |

|1908 M.|| 56 | 12 }| 117 | 17 |

| F.|| 61 | 26 }| | |

|1909 M.|| 28 | 6} | 58 | 8 |

| F.|| 30 | 13} | | |

+----------++------+------+------+------+

[A] Lord James’s Code--Rule 3 onwards--came into force.

[B] Medical examination of men began.

The processes in so far as lead enters can best be divided into--(1)

Glaze; (2) decorative.

1. _Glaze Processes._--The charge of glaze is made by weighing

out and mixing carbonate of lead with the necessary silicates and

silico-borates in the lead house or mixing-room, where wet grinding

prepares the mixture for the dipping-tub. “Putters-up” hand the ware

to the dipper, from whom “takers-off” place it on boards for removal

to the drying still, or place it (in large works) directly on to the

shelf of an appliance known as a “mangle,” in which an endless chain

carries the ware through a heated chamber. Subsequently superfluous

glaze has to be removed from the base, rims, and not infrequently also

other parts of the articles. This ware cleaning is performed with a wet

sponge or flannel, either while the ware is still moist or by scraping,

the particles removed dropping into a vessel of water; or, if the glaze

is dry, over a grating provided with exhaust draught. The ware is next

removed by the glost-placer on boards, and each piece is separately

placed by him in the sagger (fireclay receptacle) and carried into an

oven to be fired.

2. _Decorative Processes._--Majolica painting is the application of a

coloured glaze rich in lead by means of a brush. Ground-laying consists

in dusting powdered enamel colour on to a pattern first printed on

glazed ware with an oily medium. Colour dusting differs from the same

only in detail.

Aerographing (colour blowing) is the blowing on to the ware, by means

of a jet of compressed air, coloured glaze, or enamel colour held

in suspension in oil or other liquid in a glaze kettle or aerograph

instrument.

_Dangers._--Apart from risk inseparable from, and increased by,

defective lighting, uneven floors of wood or brick, collection of

dust on benches and floors, and the risk entailed in the sweeping of

these even when watering is practised, and lack of care and attention

to detail on the part of the worker, the following special dangers

are incidental to the various processes: In dipping the glaze (except

in tiles, where the surface only is allowed to touch the liquid),

splashes on to the face and overalls of the dipper, “hander-up,” and

“taker-off” (dipper’s assistants), and “threader-up” (in the case

of china furniture), especially when, as with plates, there is much

shaking of the ware. These splashes dry, and the overalls may become

so coated with glaze that every movement, such as carrying boards or

leaning against the mangle, crumbles it off as dust into the air. As

the dipper shakes the ware, some of the drops are disseminated into

the atmosphere as a fine spray. In ware cleaning the work may have to

be done so rapidly that it is difficult always to observe proper care,

and the worker is tempted to withdraw the article from the range of the

exhaust. Sometimes a ware cleaner is seen blowing away with her mouth

dust lying on the ware.

Dipping-boards, unless freed from adherent glaze by washing after use,

create dust whenever ware is placed on, or removed from, them, when

they are handled and placed on or taken off the stillage bars, and when

they are stacked. Persons gathering at the mangle are exposed to dust

if there is any outward current of air from it. The glost-placer raises

a slight amount of dust as he takes the ware from the board and places

it in the sagger. The dangerous practice formerly almost universal of

rubbing the bottoms and rims of cups, etc., either together (without

use of an exhaust) or rubbing them on a piece of leather fixed round

the chest, is generally replaced by removal of the glaze on a moist

piece of flannel, but it is still possible to find men doing it in

outlying potteries. In majolica dipping and painting (apart from the

obvious risk of splashing and contamination of the hands), danger

arises mostly from scraping the edges and under surfaces of the tiles

on to which glaze, when applying the background, has overflowed. The

amount of glaze so removed is considerable, and if it is not all caught

in the trough of water, the floor becomes an added source of danger.

In all the _decorative processes_--ground-laying, aerographing,

colour-dusting, and grinding of colours for aerographing, etc., the

danger is one solely arising from dust.

_Prevention._--Meticulous attention to detail, not only in the

provision, but also in the maintenance, of the locally-applied exhaust

ventilation, alone can allay the danger in the processes to which

dust is incidental, such as ware cleaning, gathering at the mangle,

glost-placing, and the decorative processes. The Lead Committee

considered that, as there was no rapid method of testing the actual

degree of moisture, exhaust ventilation might be required in the case

of ware that was not cleaned within fifteen minutes of the application

of the glaze. Such a requirement would prevent the practice now

prevalent of painting as many as three dozen tiles, piling them one

on top of another, and then proceeding to the operation of scraping.

No danger attaches to removal of glaze with a damp sponge or flannel,

but means must always be at hand for washing and damping them. In the

dipping-house, (_a_) impervious floors should be provided, which could

be washed down so as to prevent the risks from sweeping, and from

glaze drying, and being raised as dust; (_b_) partial covering of the

dipping-tub to prevent splashing and spray; and (_c_) substitution

for the overalls at present worn by persons in the dipping-house,

glost-placers, millers and mixers of glaze, majolica paintresses, and

others, of overalls of some light waterproof material which could be

sponged, or of aprons of waterproof material worn in front of the

overalls. Dipping-tubs and walls and floors in close proximity to them

can with advantage be painted red. Dipping-boards should be washed with

clean water after every time of use. Automatic machines for washing and

scrubbing boards are in use in some factories.

To reduce risk or remove the danger of lead poisoning in this industry,

use of low solubility glazes or of leadless glazes are advocated. On

this point the Lead Committee say: “The effect of melting the lead

with silicious matter amounts to imprisoning it in such a manner as

to render it less liable to the action of the acids which it meets in

passing through the human body, and in consequence largely reduces the

likelihood of its absorption into the blood. If the frit is properly

compounded, all but a small fraction of the lead is rendered insoluble,

and glazes so made are spoken of as ‘low solubility glazes.’ The

finished glaze generally contains from 12 to 22 per cent., or more, of

lead oxide, but after the process of fritting with sufficient silicious

material only from 2 to 5 per cent. remains soluble.”[A]

[A] Raw lead comprises red lead, white lead, and litharge. If

introduced in this form as a constituent of glaze it is soluble in

dilute acids. If, however, the raw lead is fluxed by heating with a

part or the whole of the silica, it is converted into “fritted lead.”

The solubility of the frit depends upon the relative proportions of

material taken. Thorpe[23], as a result of numerous analyses of lead

silicates (after determining their solubility as regards lead), both

simple and complex, in use in the potteries and on the Continent,

found that the quantity of lead dissolved had no necessary relation

to the quantity of lead in the silicate. “Primarily and in the main

the insolubility of the lead depends not upon any one oxide or group

of oxides, but upon the maintenance of a certain proportion between

the whole of the basic oxides on the one hand and the whole of the

acidic oxides on the other. If the value of ratio bases/acids is

higher than, or approximately equal to, two, the amount of the lead

extracted is small, but if it fall much below two, the quantity of

lead dissolved begins rapidly to increase.”

On the subject of the use of leadless glazes, the Committee conclude

that in all classes of pottery ware a great many articles can be

manufactured in a very high state of perfection, with reduction in

the cost of production of certain classes of common ware, such as

jampots and Persian painted ware; but that in certain other classes,

owing to the excessive number of “seconds,” their use would entail

increased cost or sacrifice of quality, so much so as to involve loss

of important markets; and, finally, that certain kinds of ware, in

consequence of difficulties relative to accuracy in reproducing old

patterns, colours, or methods of decoration, cannot at present be made

at all without use of lead.

In the case of manufacturers who are able to conform to the Thorpe test

of low solubility--_i.e._, glaze which yields to a dilute solution of

hydrochloric acid not more than 5 per cent. of its dry weight of a

soluble lead compound, calculated as lead monoxide (PbO)--important

relaxation of certain special rules are allowed, such as limitation

placed on the employment of females and young persons, and periodical

medical examination of the workers.

H. R. Rogers[24], one of H.M. Inspectors of Factories, Stoke-on-Trent,

has worked out a simple test to show approximately how much lead has

been used in the glaze of a piece of pottery. Thus, by treating glazes

with hydrofluoric acid for forty seconds, absorbing the liquid with

filter paper, precipitating the lead on the paper as the sulphate,

dissolving out the sulphate soluble in water, and then precipitating

the lead on the paper as sulphide, stains are produced varying, in

depth of colour, according to the proportion of lead in the glazes

concerned (see Plate IV.).

Briefly summarized, the recommendations of the Potteries Committee in

regard to the processes are--

_Manufacture of Glazes._--No handling of white or red lead without at

least 5 per cent. of added moisture, and no weighing out, etc., nor

employment in the room, to be allowed within thirty minutes of such

weighing out, etc., without the wearing of a respirator.

_Lawning_--_i.e._, straining glaze so as to remove insufficiently

ground material through a fine lawn sieve--to be done by an adult male

only, except where less than a quart of glaze is lawned.

_Dipping._--Impervious floors sloped towards a drain to be cleaned by

an adult male, after work has ceased, with a jet of water and a mop.

Walls adjacent to dipping-tubs to be tiled or painted with washable

paint, and cleaned daily. Dipping not to be done where artificial light

is necessary during hours of daylight.

_Threading-up and Thimble-picking_ to be done in a room sufficiently

separated from any place where scheduled processes are carried on.

_Drying Ware after Dipping._--The same requirement as to floors as in

dipping-house.

_Boards._--To be cleaned with clean water by an adult male after each

time that dipped ware has been placed on them and before subsequent

use. Boards for use in lead processes to be painted red at the ends.

_Mangles._--Ventilation to be so arranged as to maintain a flow of air

into the hot chamber from the workroom. Mangle shelves to be thoroughly

wet cleansed once a week.

_Ware Cleaning._--Local exhaust ventilation to be applied except when

the process is carried on entirely with use of wet materials (damp

sponges, etc.), or when done within fifteen minutes of application of

glaze. Troughs to be provided to collect glaze, and to be cleaned out

and supplied with fresh water at least once a week. The floors and

standard of lighting to be the same as for the dipping-house.

_Glost-placing._--Boards to be treated as already described. Floors

to be impervious. Women, young persons, and children to be excluded,

except that women to be allowed to place china furniture and electrical

fittings.

_Majolica Painting and Mottling._--A sponge and clean water to be

placed beside each paintress; special washing accommodation in the

painting-room or adjoining it; splashes to be removed immediately

by wet sponging. Work-benches and floors to be subject to the same

conditions as potters’ shops.

_Flow Material_--_i.e._, the substance usually containing much lead in

the form of powder and placed in the sagger to cause certain colours

applied to biscuit ware to run slightly--to be weighed out in front of

an exhaust draught and delivered to the glost-placer by an adult male.

PLATE IV

[Illustration: FIG. 1.--NO LEAD USED.]

[Illustration: FIG. 2.--FRITTED LEAD USED.

0·9 per cent. solubility.]

[Illustration: FIG. 3.--FRITTED LEAD USED.

1·5 per cent. solubility.

13·9 per cent. total lead.]

[Illustration: FIG. 4.--FRITTED LEAD USED.

5·0 per cent. solubility.

5·0 per cent. total lead.]

[Illustration: FIG. 5.--RAW LEAD USED.

19·4 per cent. solubility.

19·4 per cent. total lead.]

[Illustration: FIG. 6.--RAW LEAD USED.

44·1 per cent. solubility.

45·2 per cent. total lead.]

[Illustration: FIG. 7.--ROCKINGHAM (RAW LEAD) USED.

50·9 per cent. solubility.

50·9 per cent. total lead.]

Ground-laying, colour-dusting, and aerographing to be done under

locally applied exhaust ventilation. Proper receptacles to be

provided for cotton-wool used and waste cotton-wool to be burnt. No

short-sighted person to be employed to do either glaze or colour

blowing, unless wearing suitable glasses, and certificate to this

effect to be entered in the Health Register.

=Litho-Transfer Making[25].=--Transfers for the decoration of

earthenware and china are made in special factories, of which there

are seven, employing 257 persons. The patterns are impressed in the

ordinary chromo-lithographic fashion, but as the enamel colours,

containing high percentages of lead, are dusted either mechanically in

the machine, or by hand by means of a pad of cotton-wool, danger from

dust is great in the absence of maintenance of a negative pressure

inside the dusting machine and an efficient exhaust draught behind the

bench where the final dusting with flour, to remove the superfluous

colour, is done. In one factory, before a fresh colour was applied to

the adhesive pattern on the sheets, the machines had to be cleaned

as far as possible of the previous colour used. To do this it was

necessary for the attendant to enter a closed chamber at the back of

each machine, so as to supply the powder to the hoppers which feed the

rollers, or to clean them by means of a brush, sometimes as often as

every half-hour. The upward exhaust ventilation applied to the interior

of the machine tended to draw the dust created in brushing past the

worker’s face, and led to severe incidence of poisoning. The remedy

suggested by Pendock[26] was to dispense altogether with the need for

entering the chamber, to maintain a slight negative pressure inside the

machine by downward exhaust, and to remove the dust by means of a small

vacuum cleaning plant.

At the same factory the flouring bench was in the same room as the

machines, and the locally applied exhaust drew its air-supply from the

general atmosphere of the room. Apart from faulty arrangement of the

exhaust ducts leading to effects of too local a character, dust was

drawn from other parts of the room, including the machines, so much

so as to necessitate frequent cleaning of the glass hoods. Poisoning

among those employed in flouring occurred. To remedy this, an air-grid

with curved inlets at intervals of 2 inches apart, leading into a trunk

in connection with a fan, was placed along the back of the bench and

under the top of the glass hood. In order, however, that its action

should not interfere unduly with the general ventilation of the room,

but be, in large measure, independent of this, a somewhat similar grid,

introducing air from the street outside, was fitted along the front

of the bench. The whole arrangement was operated by one suction fan.

Ten cases occurred in this factory in the year before this arrangement

was carried out. In the three years since, three cases only have been

reported. In the ten years 1900-1909, 48 cases were reported among 257

persons employed.

=Vitreous Enamelling[27].=--Surfaces, such as sheet iron for

advertisement signs, cast iron for baths and gas stoves, copper

for copper letters and tablets, brass for jewellery, and glass for

lettering and decoration, are treated with glaze or enamel colours,

which, either in the mode of application or subsequent treatment before

final vitrefaction, give rise to dust.

In the manufacture of advertisement signs, glaze is swilled on to the

sheet of iron. After drying, it is fired or vitrified, and upon this

surface as many other coats of glaze are applied as may be wanted. As

soon as the colour is dry, lettering is effected by brushing away the

dried (but not fired) glaze exposed through stencils.

_Dangers and Prevention._--Exhaust ventilation for the removal of

the dust is essential, but it is, unfortunately, unable to draw the

dust away when brushing is done at a distance of more than about 18

inches from the exhaust opening. And some of the plates required are

very large. No exhaust-pipe has yet been invented which will follow

the hand of the worker without impeding movement. In consequence of

severe incidence of poisoning, mainly on young women who do the work

of brushing, when the process was first introduced with enamel glazes

containing from 15 to 75 per cent. of lead, manufacturers quickly

turned their attention to use of enamels free from lead. For this class

of work they appear to have been entirely successful, and now lead

poisoning is almost a thing of the past. Thus, of 122 samples examined

in 1910 from factories claiming exemption from the regulations by

reason of the use of enamels containing less than 1 per cent. of lead,

excess was found in three only[28].

=Porcelain Enamelling.=--The cast-iron bath or stove is heated to

redness in a muffle furnace. On withdrawal from the furnace it is

placed by the helpers on a table capable of being turned in every

direction. Enamel powder is then dusted on to the heated metallic

surface through a sieve attached to a long wooden handle, held by the

duster, who protects himself from the intense heat by a mask and an

asbestos cloth covering.

[Illustration: FIG. 12.--The first glaze is sprayed on with an

aerograph. The portion of the stove to be glazed is shown on supports

on the sliding table, which is half out of the cabinet. When the

casting is fully in the cabinet, the end piece and the centre piece

close the cabinet sides, and, fitting on a felt beading, make an

air-tight joint. The spray, shown in front of the cabinet, is worked

through the holes in the glass front. Exhaust is provided at the top.]

_Dangers and Prevention._--The heated column of air carries up much

of the powdered glaze as it is unevenly distributed by jolting the

handle of the receptacle, and in the absence of very efficient exhaust

ventilation this dust will, as the current of air strikes the roof and

cools, fall down again. The hood placed over the bath must have steep

sides and be brought down as low as is possible without interfering

with work, and the duct leading to the fan must be unusually wide, so

as to be able to cope with the up-rush of heated air. If the sides

of the hood be shallow, not only will the dust fail to be removed,

but the hood itself may become so hot as noticeably to increase the

discomfort from heat to which the men are exposed during the three or

four minutes, five or six times an hour, that the dusting operation

lasts. A method has been patented by M. Dormoy of Sougland[29], Aisne,

France, for carrying out automatically in a closed chamber the process

of dusting on to small red-hot castings, such as are required in the

manufacture of stoves. It is not applicable for baths.

Occasionally, in the case of small castings, again, the enamel is

sprayed on by means of an aerograph. For this excessively dangerous

process we have seen simple and ingenious devices for carrying it on

quite safely in a space under negative pressure, and covered in except

for the necessary openings through which to work the spray (see Figs.

12, 13, 14).[A]

[A] The cabinets have been patented by Messrs. Wilsons and

Mathiesons, Ltd., Leeds, by whom they are made and supplied. Since

using them there has been no trace of illness among the persons

employed.

[Illustration: FIG. 13.--After firing the casting is lifted out for

treatment with dry glaze, which is sprinkled on with a sifter shown on

the table. The turntable enables the operator to manipulate the red-hot

casting more easily.]

White enamel powders free from lead are used entirely by some firms,

but the black and coloured enamels on stove grates contain lead. A frit

analyzed in the Government Laboratory was found to contain 26·66 per

cent. of lead oxide. The fact that all the lead used is in the form of

a silicate, even although the silicate is readily soluble in dilute

acid, tends, we believe, to cause incidence of poisoning to be less

than might have been expected from the amount of dust often present in

the air, and attacks, when they occur, to be less severe, as a rule,

than they would be were raw carbonate of lead alone used. For the

arduous work entailed the men are specially selected. Despite their

exposure to lead dust, the majority continue to work for many years

without marked signs of lead absorption. The management should provide

a suitable room for the men to cool themselves in the intervals of

dusting.

[Illustration: FIG. 14.--The cabinet is shown when dry dusting is being

done. The casting is worked by tongs through a slot in the side of the

cabinet (not seen), while the worker dusts the casting with his arms

through the two front holes. He can see his work through the square

pane of glass. (Photographs kindly made by Mr. F. W. Hunt, Leeds.)]

=Manufacture of Electric Accumulators[30].=--Electric accumulators

are secondary batteries which serve for the storage of electricity,

in order to allow of a current when desired. A primary battery is

one in which the materials become exhausted by chemical action, and,

unless a portion or the whole of the materials is renewed, fails to

supply electricity. The secondary battery becomes exhausted in the

same way, but the chemical contents are of such a nature that it is

merely necessary to pass a current of electricity through the battery

(charging) in order to recharge them. In the accumulator battery the

positive element is peroxide of lead, and the negative element spongy

lead. The elements--several positive connected together and several

negative--are placed in dilute sulphuric acid contained in vessels of

glass.

The form of accumulator in almost universal use now is the pasted

plate, but it varies greatly in size, according to the use for which

it is required. It may be either large, to act as an equalizer or

reservoir of current in electric-lighting installations, or quite small

for ignition purposes in motor-cars. The litharge smeared on to one

plate becomes converted into the positive element, peroxide of lead,

during what is called the “forming process” (passage of the electric

current through the dilute sulphuric acid solution in which it is

placed), and red lead smeared on to the other becomes spongy lead to

form the negative.

The industry gives employment to about 1,200 persons. Plates are first

cast in moulds from a bath containing molten lead or of lead with

admixture of antimony. Irregularities in the plates so cast are removed

by a saw or knife (trimming), and sometimes filed or brushed with a

wire brush. The interstices in the plates are next filled in by means

of a spatula with paste of litharge or red lead, as the case may be,

which has been previously mixed either by hand at the bench or in a

special mechanical mixing machine. After drying, the plates are removed

to the formation room to be charged. To allow of the passage of the

current, positive elements are connected together, and negative also,

by means of a soldering iron or, more frequently, of an oxy-hydrogen

blowpipe flame. After formation is complete the plates have to be

built into batteries, or “assembled.” Tailpieces, technically known as

“lugs,” have to be connected with each plate, effected usually by the

oxy-hydrogen blowpipe flame. Finally, a connecting bar of lead is cast

on or burnt on to the lugs.

_Dangers and Prevention._--In casting, danger is mainly from dust in

depositing the skimmings, and from fume also when old accumulator

plates are melted down. For these reasons exhaust ventilation over the

melting pots should be provided, embracing also (by branch ducts if

necessary) the receptacles into which the lead ashes are thrown. In

mixing and pasting, the danger is from dust of oxides of lead to be

controlled (see Fig. 6) by--(1) Exhaust ventilation by branch ducts

protecting (_a_) the barrel from which the material is scooped, (_b_)

the mechanical mixer into which the weighed quantity of oxide is

discharged, (_c_) the bench at which the mixing by hand is done; (2)

dampness of benches and floor to prevent raising of dust either by

manipulation of the (often) heavy plates or trampling into powder the

paste which may fall on the ground.

In assembling or putting together of the formed plates, and in earlier

stages of the manufacture also, filing or use of a wire brush causes

production of metallic lead dust and of the oxides when the brush

touches them--a danger only to be met by exhaust ventilation. How far

the poisoning to which the lead burners engaged in assembling plates

is attributable to lead fume, produced by the high temperature of the

blowpipe flame, and how far to handling (with inevitable dislodgment of

dust) has not been satisfactorily settled. Incidence of poisoning on

this class of worker in the past has been marked.

By the _roast and reaction method_ a part of the galena is first