sulfuric acid, the other one filled with a hyposulfite solution of known
strength. The middle tubule serves to introduce a glass tube through
which carbon dioxid or illuminating gas passes for the purpose of
driving out the air from the solution and the flask. If carbon dioxid be
used it should be generated by the action of sulfuric acid on marble.
The cork holding this is furnished with a slot or valve to permit the
exit of the air and the excess of the gas.
Before inserting the middle stopper, a few cubic centimeters of
potassium iodid solution and a few drops of thin starch paste are added,
the potassium salt being always used in excess of the nitrite supposed
to be present.
[Illustration:
FIGURE 89. METHOD OF CHABRIER.
]
After the air has all been expelled from the flask the analytical
process is commenced, the carbon dioxid current being slowly continued.
At first, a few drops of the dilute sulfuric acid are allowed to flow
into the flask. As soon as the liquid is colored blue a sufficient
quantity of the thiosulfate solution is added to discharge the color.
The successive addition of acid and thiosulfate is continued until
another portion of the acid fails to develop the blue color, thus
indicating that all the nitrite has been decomposed. From the volume of
thiosulfate used the quantity of nitrite is calculated.
_The Thiosulfate Solution._—The thiosulfate solution is conveniently
prepared, when a large number of analyses is to be made, by dissolving
twenty-five grams of pure crystallized sodium thiosulfate in 100 cubic
centimeters of water and diluting any convenient part thereof to 100 or
1,000 cubic centimeters, according to the supposed strength of nitrite
solution under examination.
For fixing the strength of the solution dissolve 3 348 grams of pure
iodin in a solution of potassium iodid and make the volume up to one
liter. Each cubic centimeter of this solution corresponds to one
milligram of nitrous acid. A given volume of the iodin solution is
titrated against the thiosulfate, but it is best not to add the starch
paste until the greater part of the iodin has been removed. The starch
paste is then added and the titration continued until the blue color has
been discharged. Ten cubic centimeters of the iodin solution is a
convenient quantity for the titration and the thiosulfate should be
diluted by adding to ten cubic centimeters of the solution mentioned
above, 990 cubic centimeters of water. Each liter of this dilute
solution contains two and a half grams of the sodium thiosulphate.
_Example._—Let us suppose that it has required 21.3 cubic centimeters of
thiosulfate to absorb ten cubic centimeters of the iodin solution;
further that ten liters of water have been evaporated and titrated as
described above, and that the volume of thiosulfate employed was 13.8
cubic centimeters. From this is derived the following formula: (13.8 ×
10)/(21.3) = 6.48 milligrams of nitrous acid; or 0.648 milligram per
liter.
=508. Estimation of Nitrous Acid By Coloration of Solution of Ferrous
Salt.=—This method, due to Picini is based on the production of the
well-known brown color formed by the action of nitric oxid on a ferrous
salt.[339] The nitrite is decomposed by heating with acetic acid while
nitrates thus treated do not develop the reaction. The tint produced is
imitated as above by testing against a standard solution of nitrite.
Ferrous chlorid is to be preferred to other ferrous salts for the above
purpose. The process should be carried on in solutions free of air.
=509. Estimation of Nitrous Acid By Decomposition with Potassium
Ferrocyanid.=—The method of Schaeffer was first described in 1851, but
little attention has been paid to it since. The method has lately been
brought into notice again by Deventer.[340]
The reaction depends upon the decomposition of nitrous acid by potassium
ferrocyanid in the presence of acetic acid with the formation of
potassium ferricyanid and acetate, and nitric oxid. The reaction is
expressed by the following equation:
2K₄FeCy₆ + 2HNO₂ + 2C₂H₄O₂
= K₆Fe₂Cy₁₂ + 2KC₂H₃O₂ + 2NO + 2H₂O.
[Illustration:
FIGURE 90.
SCHAEFFER’S NITROUS ACID METHOD.
]
A eudiometer with a glass stop-cock is arranged as shown in Fig. 90. The
lower part of the eudiometer is closed with a rubber stopper carrying a
glass tube which ends in the pan _f_ as shown at _e_. The eudiometer is
filled to the stop-cock with a solution of potassium ferrocyanid of
about fourteen per cent strength. The dish _f_ is also filled up to the
height indicated in the figure with the same solution. The solution of
nitrite is used in such quantities that the nitric oxid evolved will
occupy a space of about twenty cubic centimeters. The whole eudiometer
should contain about fifty-seven cubic centimeters. The nitrite solution
is added to the eudiometer by means of a funnel, _a_. The vessel
containing it is washed out with a little water and then with acetic
acid and finally with a few cubic centimeters of strong potassium
ferrocyanid solution. The last fluid flows through the solution of
nitrite and acetic acid and thus mixes it with the solution already in
the eudiometer. The liquids reacting on each other float together on the
strong ferrocyanid solution and each one of them is at once pressed
downward by the gases which are evolved. When the evolution of gas
becomes slower the apparatus should be shaken for about twenty minutes,
moving it back and forth without taking the bottom of it out of the
dish. When there is no longer any evolution of gas, water is added
through a slowly, until the heavy potassium ferrocyanid solution is
almost completely driven out of the eudiometer. The opening of the tube
at _e_ is then closed with the thumb, the apparatus is taken out of the
dish, shaken for some time in a vertical direction and again placed in
the dish. Water of any required temperature is now allowed to flow
through the jacket, _g_, _h_, until the temperature is constant, when
the volume of nitric oxid is read. The whole experiment can be performed
in less than an hour. Operating in this way, at the end there is in the
eudiometer a liquid which is not very different from water and one whose
coefficient of solubility for nitric oxid is practically the same as
that of water. The gas volume read is to be corrected for temperature,
pressure, tension of the aqueous vapor, height of the water column in
the eudiometer, and, after the end of the calculation, five per cent of
the volume of water remaining in the eudiometer is to be added to the
volume of gas obtained. This is to compensate for the volume of the gas
absorbed by the water. The method gives good quantitive results.
=510. Method of Collecting Samples of Rain Water for
Analysis.=—Warington collects rain water in a large leaden gauge having
an area of 0.001 of an acre.[341] Of the daily collection of rain, dew,
and snow water, an aliquot part amounting to a gallon for each inch of
precipitation is placed in a carboy; at the end of each month the
contents of the carboy are mixed, and a sample taken for analysis. In
the carboy receiving the rain for nitric acid estimation a little
mercuric chlorid is placed each month with the view of preventing any
change of ammonia into nitric acid. It may be doubted, however, if this
precaution is necessary, as the rain water thus collected always
contains a very appreciable amount of lead; and experiments have shown
that on the whole, rain water more frequently gains than loses ammonia
by keeping.
_Preparation of the Sample._—The method first employed by Warington was
to concentrate ten pounds of the rain water in a retort, a little
magnesia being used to decompose any ammonium nitrite or nitrate
present. Concentration by evaporation in the open air, and especially
over gas, results in a distinct addition to nitrites present. When
concentrated to a small bulk, the water is filtered and evaporated to
dryness in a very small beaker. The nitrogen as nitrates and nitrites is
then determined by means of the methods already described.
DETERMINATION OF FREE AND ALBUMINOID AMMONIA IN RAIN AND DRAINAGE WATERS
AND SOIL EXTRACTS.
=511. Nessler Process.=—The quantities of free ammonia in rain and most
drainage waters are minute, but may reach considerable magnitude in some
sewages. By reason of these minute proportions, gravi- and volumetric
methods are not suitable for its quantitive determination. Recourse is
therefore had to the delicate colorimetric reaction first proposed by
Nessler. This reaction is based on the yellowish-brown coloration
produced by ammonia in a solution of mercuric iodid in potassium iodid.
The coloration is due to the formation of oxydimercuric ammonium iodid,
NH₂Hg₂OI, and takes place between the molecule of free ammonia and the
mercuric iodid dissolved in the alkaline potassium iodid as represented
by the following equation:
Hg—O—Hg—I Hg
/ / \
O + 2H₂N = 2O NH₂I + H₂O
\ \ /
Hg—O—Hg—I HG
_Nessler Reagent._—Dissolve thirty-five grams of potassium iodid in 100
cubic centimeters of water. Add to this solution gradually a solution of
seventeen grams of mercuric chlorid in 300 cubic centimeters of water
until a permanent precipitate of mercuric iodid is formed. Add now
enough of a twenty per cent solution of sodium hydroxid to make 1000
cubic centimeters.
The mixed solutions, at room temperature, are treated with additional
mercuric chlorid until the precipitate formed, after thorough stirring,
remains undissolved. This precipitate is then allowed to subside, and
when the supernatant liquid is perfectly clear, it is decanted or
filtered through asbestos and kept in a well-stoppered bottle in a dark
place. The part in use should be transferred to a smaller bottle as
required. The solution should be made for a few days before using, since
its delicacy is increased by keeping. The nessler reagent should show a
faint yellow tint. If colorless it is not delicate, and shows the
addition of an insufficient quantity of mercuric chlorid. When properly
prepared, two cubic centimeters of the reagent poured into fifty cubic
centimeters of water containing 0.05 milligram of ammonia will at once
develop a yellowish-brown tint.
_Preparation of Ammonia-Free Water._—To pure distilled water add pure,
recently-ignited sodium carbonate, from one to two grams per one liter,
and distill. When one-fourth of the whole has passed over, the
distillate may be regarded as free from ammonia; fifty cubic centimeters
of the following distillate should give no reaction with the nessler
reagent. The distillation should be continued until the residual volume
in the retort is about one-fourth of the original, and the distillate
free of ammonia is carefully preserved in close glass-stoppered bottles
previously washed with ammonia-free water. Pure water, free of ammonia
may also be obtained by distilling with sulfuric acid.
_Comparative Solution of Ammonium Chlorid containing 0.00001 gram
Ammonia in one cubic centimeter._—Dissolve 3.15 grams H₄NCl in
ammonia-free water and make the volume up to one liter. Take ten cubic
centimeters of the above solution and dilute to 1000 with water, free
from ammonia.
_Solution containing 0.00001 gram Nitrogen in one cubic
centimeter._—Dissolve 3.82 grams H₄NCl in water, free from ammonia and
dilute with same to 1000 cubic centimeters. Dilute ten cubic centimeters
of the above solution to 1000.
_The Distillation._—Any kind of suitable retort or flask connected with
a good condenser may be used. The capacity of the retort should be from
700 to 1,000 cubic centimeters. The retort and condenser preferred by
Leffmann and Beam are shown in Fig. 91. Any good lamp may be used in
which the flame is under complete control. The gauze burner shown in the
figure is easily controlled and distributes the heat evenly over the
surface of the retort thus diminishing the danger of fracture. The
apparatus having been previously rinsed with distilled water receives
500 cubic centimeters of the liquid to be tested for ammonia, together
with a few pieces of recently ignited pumice stone to prevent bumping
and five cubic centimeters of the twenty percent sodium carbonate
solution to render its contents alkaline. The water is raised to the
boiling-point and with gentle ebullition fifty cubic centimeters of
distillate collected. The distillate is conveniently collected in a
color-comparison cylinder of thin white glass and flat bottom, about two
and a half centimeters in diameter, and marked at fifty and one hundred
cubic centimeters. Two cubic centimeters of the nessler reagent are
added and if ammonia be present a yellowish-brown color will be
developed, the intensity of which is matched by taking portions of the
ammonium chlorid solution, diluting to fifty cubic centimeters with pure
water and treating with the same quantity of the nessler reagent. The
process is repeated until a distillate is obtained which gives no
reaction for ammonia. The sum of the quantities obtained in the several
distillates gives the total amount of ammonia in the 500 cubic
centimeters of the water taken. In most cases practically all the
ammonia is obtained in three or four portions of the distillate.
[Illustration:
FIGURE 91. RETORT FOR DISTILLING AMMONIA.
]
_Albuminoid Ammonia._—The residue from the process just described is
employed for the purpose of determining the albuminoid ammonia. Two
hundred grams of potassium hydroxid and eight grams of potassium
permanganate are dissolved in 1,000 parts of distilled water. Fifty
cubic centimeters of the solution are placed in a porcelain dish with
100 cubic centimeters of distilled water and evaporated to fifty cubic
centimeters. This liquid is placed in the retort and the distillation
resumed and continued until an ammonia-free distillate is obtained. The
total albuminoid ammonia is determined by taking the sum of the
quantities in the several distillates.
=512. Nessler Reagent of Ilosvay.=—To secure greater delicacy in
nesslerizing, Ilosvay uses a reagent prepared as follows:[342]
Dissolve two grams of potassium iodid in five cubic centimeters of
water, heat the solution gently, and add three grams of mercuric iodid.
After the solution is cooled, add an additional portion of three grams
of the mercury salt, and then twenty cubic centimeters of water, and
wait until the precipitation is complete. After filtering, there are
added to the filtrate from twenty to thirty cubic centimeters of a
twenty per cent solution of potassium hydroxid. Only the limpid
supernatant liquid is used in the analytical work. With this reagent,
Ilosvay has been able to detect 0.02 milligram of ammonia in 110 cubic
centimeters of water.
AUTHORITIES CITED IN PART SEVENTH.
Footnote 274:
Comptes rendus, Tome 84, pp. 301, et seq. Journal of the Chemical
Society, (Transactions), 1878, p. 44; 1879, p. 429; 1884, p. 637.
American Chemical Journal, Vol. 4, p. 452. Proceedings of the American
Association for the Advancement of Science, Vol. 41, p. 105. Annales
de l’Institut Pasteur, Tome 4, pp. 218, 257, 760; Tome 5, p. 92.
Footnote 275:
Comptes rendus, Tome 118, p. 604.
Footnote 276:
Bulletin de la Academie royale de Belgique, [3], Tome 25, p. 727.
Journal of the Chemical Society, (Abstracts), June, 1894, p. 248.
Footnote 277:
Chemical News, Oct. 13, 1893, p. 176.
Footnote 278:
Comptes rendus, Tome 109, p. 883.
Footnote 279:
Op. cit. supra, Tome 89, pp. 891, et seq.
Footnote 280:
Journal of the Chemical Society, (Transactions), Vol. 45, pp. 645, et
seq.
Footnote 281:
Jahresbericht der Agricultur Chemie, 1881, S. 43.
Footnote 282:
Annual Report of the British Board of Health, 1883.
Footnote 283:
Annales de l’Institut Pasteur, 1891, S. 93.
Footnote 284:
Philosophical Transactions of the Royal Society of London, Vol. 181,
(1890).
Footnote 285:
Zeitschrift für Biologie, Band 9, S. 172.
Footnote 286:
Archives de Science Biologique à St. Petersbourgh, Tome 1, p. 1331.
Footnote 287:
Annales de l’Institut Pasteur, 1891, pp. 581, et seq.
Footnote 288:
Op. cit. supra, 1891, Plate 18, Fig. 2.
Footnote 289:
Op. cit. supra, 1891, pp. 595, et seq.
Footnote 290:
Op. cit. supra, 1891, Plate 18, Fig. 1.
Footnote 291:
Journal of the Chemical Society, (Transactions), 1891, pp. 498, et
seq.
Footnote 292:
Annales de l’Institut Pasteur, 1891, pp. 605, et seq.
Footnote 293:
Journal of the Chemical Society, (Transactions), 1882, p. 357.
Footnote 294:
Annales de Chimie et de Physique, 1854, Tome 40, p. 479. Zeitschrift
für analytische Chemie, 1870, S. 24; 1877, S. 291. Die
Landwirtschaftlichen Versuchs-Stationen, Band 12, S. 164. Journal of
the Chemical Society, (Transactions), 1880, p. 468; 1882, p. 345;
1889, p. 537.
Footnote 295:
Encyclopedie Chimique, Tome 4, p. 151.
Footnote 296:
Annales de la Science Agronomique, 1891, pp. 263, et seq.
Footnote 297:
Berichte der deutschen chemischen Gesellschaft, Band 23, S. 1361.
Footnote 298:
Zeitschrift für analytische Chemie, Band 9, S. 24, 401. Die
Landwirtschaftlichen Versuchs-Stationen, Band 9, S. 9. Berichte der
deutschen chemischen Gesellschaft, Band 6, S. 1038.
Footnote 299:
Zeitschrift für analytische Chemie, Band 33, S. 200.
Footnote 300:
Apotheker Zeitung, 1891, Band 5, S. 287.
Footnote 301:
Sutton’s Volumetric Analysis, 3d edition, p. 316. Warington, Journal
of the Chemical Society, (Transactions), 1879, p. 376.
Footnote 302:
Report of the National Board of Health, 1882, p. 281.
Footnote 303:
Berichte der deutschen chemischen Gesellschaft, Band 11, S. 432.
Footnote 304:
Bulletin de la Société Chimique, [3], Tomes 11–12, p. 625.
Footnote 305:
Encyclopedie Chimique, Tome 4, p. 154.
Footnote 306:
Zeitschrift für analytische Chemie, Band 7, S. 412. Fresenius,
Quantitative Analysis, Grove’s translation, special part, p. 118.
Footnote 307:
Journal of the Chemical Society, (Transactions), 1879, pp. 578, et
seq.
Footnote 308:
Bulletin 38, Department of Agriculture, Division of Chemistry, p. 204.
Footnote 309:
Die Landwirtschaftlichen Versuchs-Stationen, Band 41, S. 165.
Footnote 310:
Chemiker Zeitung, 1892, Band 16, S. 1952.
Footnote 311:
Zeitschrift für angewandte Chemie, 1893, S. 161.
Footnote 312:
Chemiker Zeitung, 1889, No. 15.
Footnote 313:
Vid. op. cit. 38, 1890, S. 695.
Footnote 314:
Archives de la Société Physique de Genève, Tome 31, p. 352.
Footnote 315:
Chemiker Zeitung, 1890, S. 1410.
Footnote 316:
Chemisches Centralblatt, 1890, Band 2, S. 926.
Footnote 317:
Vid. op. cit. 38, 1891, S. 241.
Footnote 318:
Vid. op. cit. 34, 1889, p. 538.
Footnote 319:
Op. cit. supra, 1881, p. 100.
Footnote 320:
Op. cit. supra, Vol. 57, p. 811.
Footnote 321:
Op. cit. supra, 1891, pp. 530, et seq.
Footnote 322:
Op. cit. supra, 1874, p. 630, and 1885, p. 86.
Footnote 323:
Sutton’s Volumetric Analysis, 4th edition, p. 103.
Footnote 324:
American Journal of Science, Vol. 44, p. 117.
Footnote 325:
American Chemical Journal, Vol. 11, p. 249.
Footnote 326:
Journal of the Franklin Institute, Vol. 127, p. 61.
Footnote 327:
Zeitschrift für Hygiene, Band 2, S. 163.
Footnote 328:
Chemical News, 1889, Nov. 29, 261.
Footnote 329:
Vid. op. cit. supra, p. 51.
Footnote 330:
Examination of Water for Sanitary and Technical Purposes, p. 28.
Footnote 331:
Chemical News, 1890, Jan. 10, p. 15.
Footnote 332:
Zeitschrift für angewandte Chemie, 1894, Heft 12, S. 347.
Footnote 333:
Journal of the Chemical Society, (Abstracts), 1891, p. 489.
Footnote 334:
Zeitschrift für analytische Chemie, Band 18, S. 597. Zeitschrift für
angewandte Chemie, 1889, S. 666. Bulletin de la Société Chimique, [3],
Tome 2, p. 347.
Footnote 335:
Op. cit. 57, p. 30.
Footnote 336:
Zeitschrift für angewandte Chemie, 1894, S. 349.
Footnote 337:
Bulletin de la Société Chimique, [3], Tomes 11–12, p. 218.
Footnote 338:
Encyclopedie Chimique, Tome 4, p. 262.
Footnote 339:
Peligot, Traité de Chimie Analytique appliqueè à Agriculture, p. 261.
Footnote 340:
Berichte der deutschen chemischen Gesellschaft, 1893, S. 589.
Footnote 341:
Journal of the Chemical Society, 1889, p. 537.
Footnote 342:
Op. cit. 64, p. 216.
NOTE.—On page 158, paragraph 172, third line, insert, “and determining
matters dissolved therein,” after “flow.”
PART EIGHTH.
SPECIAL EXAMINATION OF WATERS, VEGETABLE SOILS, AND UNUSUAL SOIL
CONSTITUENTS.
=513. Further Examination of Waters.=—Having described in the preceding
part the approved methods of determining the oxidized nitrogen in waters
and soil extracts there remains to be considered the examination of
waters for other substances of importance to agriculture. Rain waters
add practically nothing to the soil but nitric acid and ammonia, and,
therefore, demand no further discussion here. In drainage and sewage
waters, in addition to the oxidized nitrogen, there may be sufficient
quantities of phosphoric acid and potash to make their further analysis
of interest. But by far the most practical point to be considered is in
the case of waters used for irrigation purposes where the continued
addition to the soil of mineral matters may eventually convert fertile
fields into barren wastes. In irrigated lands there is practically no
drainage and the whole of the water is removed by superficial
evaporation. It is easily seen how these mineral matters tend to
accumulate in that part of the soil in which the rootlets of plants seek
their nourishment.
=514. Estimation of Total Solid Matter.=—The total solid contents of a
sample of water are determined by evaporating a known volume or weight
to dryness and weighing the residue. For comparative purposes a given
volume of water may be taken if the solid contents do not exceed four
grams in a United States gallon. The water should be measured at a
temperature of about 15°.5. Where the content of mineral matter is
greater it is best to weigh the water and calculate the solid contents
to parts per one hundred thousand. For practical purposes in the United
States it is customary to state the content of solid matter in grains
per gallon. Since, however, the gallon has so many different values it
is always necessary to indicate what particular measure is meant.
In ordinary spring and well waters the volume to be used is conveniently
taken at 100 cubic centimeters. To avoid calculation a volume in cubic
centimeters corresponding to some decimal part of a gallon in grains may
be taken and the weight in milligrams will then be equivalent to the
grains per gallon. Thus in the imperial gallon which contains 70,000
grains of distilled water at 15°.5, seventy cubic centimeters may be
taken. If the residue weigh twenty-five milligrams the water contains
twenty-five grains of solid matter per gallon. The United States gallon
at 15°.5 contains 58,304 grains of distilled water. In this case 58.3
cubic centimeters should be used, or double this amount and the weight
in milligrams be divided by two.
The evaporation may be made in a platinum, porcelain, or aluminum dish,
preferably with a flat bottom; The dish does not need to hold the whole
volume at once, but the water may be added from time to time as the
evaporation continues. The dish, however, should, as a rule, hold not
less than 100 cubic centimeters. The evaporation is best conducted over
a steam-bath, and after the complete disappearance of the liquid the
heating should be continued until the residue is perfectly dry.
In the case of mineral waters highly impregnated with inorganic salts, a
smaller volume or weight may be taken, and greater care must be
exercised in drying the residue. For the purpose of qualitively
determining the percentage of special ingredients, quantities of the
water should be taken inversely corresponding to the content of the
ingredient desired. In general, it will not be necessary to evaporate
the sample to complete dryness, but only to concentrate it to a volume
convenient for the application of the analytical process. Where a
complete quantitive analysis of the solid residue is desired, a
sufficient quantity of the water is evaporated to give a weighable
amount of the least abundant ingredient. The total solid content of the
water having been previously determined, the actual weight or volume of
the water taken to obtain the above residue is of no importance.