Joseph William Mellor.

A comprehensive treatise on inorganic and theoretical chemistry (Volume 2) online

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Lehrbuch der Salinenkunde, Berlin, 2. 52, 1847 ; G. J. Mulder, Bijdragentot de geschiedenis van Jiet
scheikundig gebonden water, Rotterdam, 35, 49, 1864; D. Page and A. D. Keightley, Journ.
Chem. Soc., 25. 666, 1872 ; A. Levol, Journ. prakt. Chem., (1), 36. 30, 1845 ; J. H. van't Hoff
and L. T. Reicher, Zeit. phys. Chem., 3. 482, 1889 ; W. Meyerhoffer and A. P. Saunders, ib.,
28. 453, 1899 ; W. C. Blasdale, Journ. Ind. Eng. Chem., 10. 344, 347, 1918 ; J. H. Hildebrand,
ib., 10. 96, 1918 ; J. H. van't Hoff, Untersuchungen und Bildungsverhdltnisse der ozeanischen
Salzablagerung, Leipzig, 220, 1912.

36 R. F. Weinland and J. Alfa, Zeit anorg. Chem., 21. 50, 1899 ; H. Zirngiebl, Zeit. Kryst.,
36. 148, 1902 ; J. C. G. de Marignac, Ann. Mines, (5), 9. 47, 1856 ; (5), 12. 44, 1857 ; (5), 15.
236, 1859 ; A. de Schulten, Bull. Soc. Min., 19. 161, 1896 ; E. Janecke, Zeit. phys. Chem., 64.
305. 343, 1908 ; B. Karandeeff, Centr. Min., 728, 1909 ; C. F. Rammelsberg, Pogg. Ann., 97.
92, 1856 ; C. Pape, ib., 139. 238, 1870 ; H. Rose, ib., 28. 120, 1833 ; C. Schultz- Sellack, Ber., 4.
113, 1871 ; A. W. Williamson, Journ. Chem. Soc., 10. 97, 1858; H. Schift, Liebig's Ann., 126.
167, 1863; G. S. Serullas, Ann. Chim. Phys., (2), 43. 117, 1830; N. A. E. Millon, ib., (3), 9.


410, 1843; S. Zinno, Repert. Pharm., 20. 449, 1871 ; C. W. Blomstrand, Zeit. tuu>r</.
10, 1891 ; C. Friedheim, ib., 2. 383, 1892 ; 0. Ruff and W. Plato, Ber., 36. 2357, 1903 ; H. Osaan,
Chem. Centr., 97, 1862 ; W. Meyerhoffer and A. P. Saunders, Zeit. phys. Chem., 31. 373, 1899 ;
A. W. Browne, Journ. Phys. Chem., 6. 287, 1902 ; F. K. Cameron, J. M. Bell, and W. 0. Robinson,
&., 11. 396, 1907 ; A. Seidell, Amer. Chem. Journ., 28. 52, 1902 ; J. H. van't Hoff, Sitzber. Akad.
Berlin, 810, 1899 ; F. A. H. Schreinemakers and G. M. A. Kayser, Chem. Weekb., 15. 120, 1918.

27. Ammonium Sulphates

A. Libavius mentioned that crystals of a compound are formed when spiritus
urines is treated with oil of vitriol, and the soln. evaporated. J. R. Glauber also
made this salt by treating volatile alkali with sulphuric acid, and he pointed out
some of its medicinal uses. For a time this salt was known as sal ammoniacum
secretum Glauberi. D. L. G. Karsten, 1 M. Sage, L. Palmieri, and 0. Popp found
ammonium sulphate occurring as mascagnite about volcanoes in the fissures of
lava, as at Vesuvius, Etna, and the Lipari Islands ; C. Schmidt and 0. Popp, in
the Doric acid fumoroles of Tuscany, etc. ; F. H. Storer, in anthracite coal ; etc.
S. D. Crenshaw found ammonium sulphate in the flue dust of kilns, using Pennsyl-
vanian anthracite as fuel ; A. Miintz and E. Laine, from the dry distillation of
turf ; R. E. Carpenter and S. E. Linder, among the reaction products of Glaus'
kiln; E. Berglund, among the products of the hydrolysis of imidosulphonic
acid ; etc.

Ammonium sulphate is produced when aqua ammonia, or ammonium carbonate,
is neutralized with sulphuric acid, a reaction studied by F. C. Hills, R. W. Wallace,
P. S. Brown, P. Spence, and T. Illingworth, etc. L. Mond treated ammonium
chloride with sulphuric acid until all the hydrogen chloride was expelled, and then
converted the resulting hydrosulphate, (NH 4 )HS0 4 , with ammonia so as to convert
it into the normal sulphate. P. de Lachomette made it by the oxidation of crystal-
lized ammonium sulphite ; and H. H. Stephens, by treating putrefied ammonia
with calcium, sodium, or ferrous sulphate, or with alum. W. Ley bold, K. Zimpell,-
0. Kausch, H. Ost, and many others have studied the preparation of ammonium
sulphate on a manufacturing scale. H. Hampel has described two continuous
processes for manufacturing ammonium sulphate from the sulphates of the potassium
salts available at Stassfurt, etc. The one process involves reactions which are
illustrated by the equation : K 2 S0 4 +Ca(N0 3 ) 2 =2KN0 3 +CaS0 4 ; CaS0 4 +2NH 3
+C0 2 +H 2 0=CaC0 3 +(NH 4 ) 2 S0 4 ; and CaC0 3 +2HN0 3 =Ca(N0 3 ) 2 +C0 2 +H 2 0.
Synthetic ammonia and nitric acid are utilized, and the by-product, potassium
nitrate, is more valuable than the ammonium sulphate. The other process is
likewise illustrated by the equations : MgS0 4 -f CaCl 2 =MgCl 2 -f CaS0 4 ; CaS0 4
+2NH 3 +C0 2 +H 2 0=CaC0 3 +(NH 4 ) 2 S0 4 ; CaC0 3 +2HCl=CaCl 2 +H 2 0-fC0 2 ;
MgCl 2 -hH 2 OMgO+2HCl. D. H. B. Wride has also discussed the manufacture of
ammonium sulphate from calcium sulphate, ammonia, and carbon dioxide.
K. Nishizawa studied the equilibrium of the five component system involving
Na 2 S0 4 , NaHS0 4 , (NH 4 ) 2 S0 4 , NH 4 HC0 3 , and H 2 0, at 15, in order to find the
best conditions for the manufacture of ammonium sulphate from sodium sulphate
by the ammonia-soda process. He found for each 1000 grms. of water, 79 '54 mols
of Na 2 S0 4 and 134*2 mols of NH 4 HC0 3 should be mixed, and there will be produced
45'82 mols of Na, 20'90 mols of HC0 3 , 79'54 mols of S0 4 , and 134'2 mols of NH 4
per 1000 mols of water at 15.

In W. Feld's process, a mixture of hydrogen sulphide and ammonia is passed
into aq. soln. of ammonium tri- and tetra-thionate whereby the polythionates
are converted into thiosulphate : (NH 4 ) 2 S 3 6 +(NH 4 ) 2 S=2(NH 4 ) 2 S 2 3 ; and
(NH 4 ) 2 S 4 6 +(NH 4 ) 2 S=2(NH 4 ) 2 S 2 3 -1-S. The latter is treated with sulphur
dioxide and re-converted into polythionate, but double the amount is obtained as
was originally omployrd : 2(NH 4 ) 2 S 2 O 3 +3S0 2 -(NH 4 ) 2 S30 +(NH 4 ) 2 Q( 4() (; . The


excess of polythionate is removed, and the soln. boiled whereby ammonium
sulphate, sulphur dioxide, and sulphur are produced : (NH 4 ) 2 S 3 6 =(NH 4 ) 2 S0 4
-f-S0 2 +S. The sulphur dioxide is utilized as indicated above, and likewise also
the sulphur which is burnt to sulphur dioxide. The reactions have been studied
by F. Raschig.

In 1781, Earl of Dundonald patented a process for the recovery of volatile
alkali produced in the distillation of coal, but nothing came of it ; then followed,
in 1837, the patent of G. D. Midgley and J. H. Kyan for the treatment of gas liquor
for its ammonia. Ammonium sulphate was once prepared by saturating raw gas
liquor directly with sulphuric acid until the yellow liquid had a milky appearance.
The neutral soln. so formed was evaporated until the salt crystallized out. The
product was generally yellow or grey, and sometimes red or blue. It contained
other ammonium salts sulphite, chloride, thiocyanate, etc. as impurity. The
impure sulphate had a much lower market value than a purer product, and the
cost of the fuel required for the evaporation rendered the process not satisfactorily
remunerative. The salt is now made by boiling ammoniacal soln. like gas liquor
with lime, and passing the ammonia which is evolved into sulphuric acid. At first,
the ammonia was generated in a simple boiler heated by a direct fire, but the wear
of the boiler and scale produced by the formation of a hard incrustation of lime
were so troublesome that improvements were soon introduced. Among the first,
was the use of steam for heating the still in which the ammonia was generated.
The steam was either blown directly into the liquor, or passed through coils placed
in the liquor ; then a combination was so arranged that a boiler at a higher level
was heated by steam from a boiler at a lower level. The volatile products were
driven from the upper boiler, and the lime treatment was conducted in the lower
boiler. As soon as the liquid in the lower boiler was exhausted, it was run off,
and the liquor from the upper boiler passed into the lower boiler, where it was
treated with lime. The upper boiler was filled with fresh liquor, which was heated
by the steam from the lower boiler. The cycle was repeated anew.

In modern continuous processes, based on the use of A. Coffey's still, the
ammoniacal liquor is run into a superheater, where it is heated previous to entering
the still. The hot liquor is mixed with lime and passed down a tower with tiers
of chambers vide Fig. 66. A strong current of steam is blown in at the bottom
of the tower and passed upwards through perforated caps in the floor of each
chamber. Fresh liquor enters at the top of the tower, and the exhausted liquor
passes away at the bottom. The gases charged with ammonia pass from the top
of the tower and are led through sulphuric acid in the saturator, where the ammonia
is absorbed. The unabsorbed carbon dioxide, hydrogen sulphide, etc., pass along
to the superheater, where they give up a large portion of their heat. This heat is
utilized to warm up the gas liquor on its way to the tower. The gases may then
pass on to the chimney, or they may be treated in an iron oxide purifier or in a
Clans' kiln. The ammonium sulphate which crystallizes from the sat. sulphuric
acid is allowed to drain. There are several different types of plant on the market
e.g. Savalle's, Feldmann's, Griineberg and Blum's, etc.

The early analyses of R. Kir wan, and of J. J. Berzelius, translated into modern
notation would be represented by (NH 4 ) 2 S0 4 .H 2 ; but later analyses by A. Ure,
E. Mitscherlich, 0. B. Kiihn, etc., indicate no water of crystallization. The
commercial salt is light grey and may be guaranteed to contain at least 24 per cent.
NH 3 ; it commonly contains a little more say, 24' 25 to 24" 75 per cent. NH 3
from 2 to 4 per cent, of moisture ; and from 0'15 to 0'4 per cent, of free sulphuric
acid theory for (NH 4 ) 2 S0 4 , 25' 76 per cent. NH 3 , 74'24 per cent. H 2 S0 4 . The
salt is used as a fertilizer, and buyers stipulate that the salt shall be free from
cyanides which act deleteriously on vegetable growths. When the colour is good,
and the moisture low, the sulphate may be sold as " white " when the required
minimum is 25'25 per cent. NH 3 . H. Fleck found samples of commercial crude
ammonium sulphate with 0*5 grin, of arsenic per kilogram.


The properties of ammonium sulphate. Ammonium sulphate can be ob-
tained in well-developed transparent crystals by evaporation in cold dry weather
under atm. press, of sat., not supersaturated, soln. The crystals belong to the
rhombic system, and, according to E. Mitscherlich, 2 have the axial ratios a:b:c
=0-5643 : 1 : 0'731 ; or, according to A. E. H. Tutton, 0'5635 : 1 : 0'7319. The
crystals are isomorphous with potassium sulphate, not only morphologically, but
also in the continuous variation in the physical properties of mixed crystals as
shown by G. Wyrouboff and E. Mallard for the optic axial angles, and by
J. W. Retgers for the sp. gr. In the series of isomorphous alkali sulphates,
A. E. H. Tutton found ammonium sulphate to fall between rubidium and caesium
sulphates with respect to solubility, mol. vol., refractive index, axial ratios, etc.
A. Fock has also investigated the equilibrium conditions of the mixed crystals
with water, and found the composition of the soln. changed continuously with the
composition of the solid phase. A. Ogg and F. L. Hop wood have calculated the
dimensions of the unit rhomb of the crystals of ammonium sulphate from the
X-radiograms, and found the lengths of the sides a, b, c of the unit rhomb
to be respectively 5-951 XlO~ 8 cm.; 10'560xlO~ 8 cm.; and 7'729xl(r 8 cm.;
while the volume is 485"71xl0~ 24 cc. There are four mols. in the elementary
cell. On comparison with the corresponding values for the isomorphic sulphates
of potassium, rubidium, and caesium, and remembering that the replacement in
the elementary cell of eight atoms of potassium by forty atoms of the four radical
groups NH 4 causes no more distension of structure than if eight atoms of rubidium
had replaced the eight atoms of potassium ; and the replacement of eight atoms
of potassium by eight atoms of caesium causes twice the distension produced by
forty atoms of the form NH 4 -radicles. This is taken as a conclusive proof against
the theory of crystal structure based on the closest packing of the constituent
atoms, and of their spheres of influence.

The earliest determination of the specific gravity of ammonium sulphate is
1'7676 by le citoyen J. H. Hassenfratz 3 at Paris in 1798. The other published data
range from 1'75 reported by H. Buignet to T773 reported by H. G. F. Schroder.
The best representative value must be near T7687, as reported by A. E. H- Tutton
at 20 (water at 4 unity). The mol. vol. by A. E. H. Tutton is 74'63 ; and
P. A. Favre and C. A. Valson find the eq. volume of the salt is 37*4 c.c. W. Spring
gives the following values for the sp. gr. of the salt at different temp, and for the
volume assumed at different temp, by unit volume of the salt at :

10 20 40 60 80 100 . . 1-7763 1'7748 1'7734 1-7703 1-7667 1-7617 1-7567
Volume . . 1-000000 1*000846 1-001667 1*003391 1-005431 1-008289 1-011191

W. Spring found an anomalous change in the sp. gr. of ammonium sulphate by
compression at 20,000 atm., but J. Johnston and L. H. Adams could detect no
change at 12.000 atm. provided the crystals are homogeneous and free from holes
and cracks. A. Michel and L. Krafft 4 found the sp. gr. of aq. soln. sat. at 15
to be 1-248 ; A. E. H. Tutton gives 1-2030 for the sp. gr. at 20 of a 35 per cent.
aq. soln. water at 4 unity. H. Schiff found at 19 :

Per cent.

(NH 4 )SO 4 . 1 5 10 15 20 25 30 40 50 . 1-0057 1-0287 1-0575 1-0862 1-1149 1-1439 1-1724 1-2284 1-2890

Mol. vol. . 57-2 58-4 60'3 62'3 64-1 67'4 70'7 72'9

The molecular volumes are by J. Traube, who also gave 74'5 for a 100 per cent,
soln. J. A. Groshans has also studied the mol. vol. of these soln. Further data
were given by C. A. Valson, S. de Lannoy, F. Kohlrausch, and R. Abegg, etc.
P. A. Favre and C. A. Valson gave T0378 for the sp. gr. of a normal soln. at 20 ;
and for the specific volume of a normal soln. at 0, 15, and 30, W. Lerche gives
I'OOOOOO, 1'00241, and 1*00661 respectively. S. de Lannoy gave for the sp. vol.
v of 4 per cent, soln., when V Q is the sp. vol. of the soln. at 0, VVQ(! 0*0000480



+0-000004640 2 ) between and 40, and v=v Q (l 0-00010590+0-000003320 2 )
between 40 and 82 ; for 12 per cent, soln., v=v Q (l O'OOOl 7230 -f 0*0000028370 2 )
between and 40, and v=v (l 0*00018650 +0*000002480 2 ) between 40 and
85; for 20 per cent, soln., v=v (l 0*00024240 +0*000001 720 2 ) between and
82; and for 50 per cent, soln., v=v (l 0*00026900 +0*0000007520 2 ) between
and 93'7. D. Dijken and A. Kanitz also made observations on the sp.
vol. of soln. of ammonium sulphate ; and 0. Pulvermacher on the sp. gr. of these
soln. S. de Lannoy gave 5*1 for the temp, of maximum density of a 4 per
cent, soln., 30*3 for a 12 per cent. soln. ; 70*4 for a 20 per cent. soln. ; and
178 for a 50 per cent. soln. P. A. Favre and C. A. Valson found that during
the soln. of an eq. of ammonium sulphate in a litre of water, the water contracts
27'3 c.c., and the contraction of the salt amounts to 10*1 c.c., so that the total con-
traction is 37*4 c.c. H. Gilbault found that at 20, w grms. of the salt dissolved
in lOOw grms. of water contracted such that if V denotes the volume of the soln.,
when v is the volume of the water and v 2 that of the salt, fli+i* 2 F=0'1120,
0'0835, 0'0583, and 0*0343, when w is respectively 10, 20, 30, and 40. The subject
is also discussed by W. Ostwald and M. Rogow.

According to W. Spring, 5 after subjecting ammonium sulphate to a press, of
20,000 atm. for three weeks the press, fell from 1*773 (20) to 1*750 (22) ; and after
a repetition of the treatment the sp. gr. was 1*760 (22). W. C. Rontgen and
J. Schneider give 0'741 and 0'853 for the relative compressibility of a soln. of a
mol. of the salt in 1,500 and 700 mols. of water respectively; and for the relative
mol. compressibility 0'808 and 0*887 respectively. P. G. Tait also measured the
compressibility of soln. of ammonium sulphate. H. Gilbault found that if a denotes
the quotient : mol. of ammonium sulphate by mol. of water ; D the sp. gr. of the
soln. at 20 (water at 4 unity) ; k is the mean, and j3 the mol. compressibility,
then for w per cent. soln. at 20 the value of (log k Q log Jc)D/a is nearly









4437 (j8 )

























Water with ammonium sulphate in soln. has a smaller sp. vol. than water.
From P. G. Tait's measurements of the press, necessary to produce a corresponding
contraction in the sp. vol. of water, G. Tammann calculated that the increase in
the internal press. P atm. of water produced by the dissolution of the salt ex-
pressed in grams of salt per 100 grms. of water, is as follows :

Grm. salt . . . . 3'34 6 '78 14 -0

Internal press. 8P, at 10 . 243 448 759

15 . 250 455 755

30 . 247 435 732


C. A. Valson gave 59' 7 mm. for the capillary rise in a tube 0*5 mm. diameter at
20. The surface tensions of a mol. of the salt in 1500 and 700 mols. of water may
be regarded as proportional to the product of the capillary rise and sp. gr., and
they were given by W. C. Rontgen and J. Schneider as 116'91 and 113'99 respectively.
H. Sentis has also studied the surface tension of ammonium sulphate soln. C. Forch
found the surface tension a (mgrm. per mm.) of soln. at containing w half a
mol. per litre :







"* "seta." 'water






































Sp. tit.

Mol. ht.

A. Kanitz gave the viscosity of N-, J2V-, %N-, and JN-soln. as respectively Til 14,
T0552, 1'0302, and T0148 (water unity). A. Kanitz also measured the viscosity
of soln. of ammonium sulphate mixed with potassium or aluminium sulphate.
R. Abegg and 0. Pulvermacher have also studied the viscosity of soln. of this salt.
T. Graham found that in 24 hrs. 0'0389 grm. diffused from an approximately
normal soln. into water J. H. Long found 0'0482 grm. J . H. Long also found
the velocity of diffusion, i.e. the relative number of mols. which diffused from a
normal soln. in a day, to be 724.

The coefficient of thermal expansion of the solid salt can be computed from
W. Spring's data indicated above, and A. de Lannoy found for 4 per cent. soln.
at 50, Q'0004374 ; at 100, 0'0007099 ; for 12 per cent, soln., 0'000434 at 50,
and 0-000682 at 100 ; for 20 per cent, soln., 0'000414 at 50, and 0'000586 at
100 ; and for 50 per cent, soln., 0'000344 at 50, and 0'000419 at 100. He also
represents his results by a formula of the type v=v (l -\-a6-\-bd 2 ) as indicated
above. G. Tammann's value for the specific heat of the solid salt is 34 Cals. per
mol. J. C. G. de Marignac gives for the sp. ht. of soln. (NH 4 ) 2 S0 4 +wH 2 at 19-51.

15 25 50 100 200

0-7385 0-8030 0-8789 0'9930 0-9633

. 297 476-3 907 1802 3595

G, Tammann, A. Winkelmann, and J. Thomson also give values for this constant.
According to R. F. Marchand, 6 the melting point of ammonium sulphate is
140 ; but this is wrong, for it really referred to the hydrosulphate ; at 280 the
salt is said to begin to vaporize, and at the same time to be decomposed with the
formation of some nitrogen and of ammonium sulphite. On a gradually rising
temp., W. Smith found that the evolution of ammonia could be detected between
120 and 125, and in some cases at as low a temp, as 80. R. Reik says that the
sublimation in vacuo as well as at ordinary temp, is attended by a transformation
of the salt into the hydrosulphate, (NH 4 )HS0 4 . W. Smith showed that the observed
fusion is not due to the melting of the normal sulphate, for this salt does not melt
but passes into the hydrosulphate, and a very pure hydrosulphate can be obtained
by heating the normal sulphate to about 320 in a platinum dish. Ammonia is
first evolved, and as the temp, rises, ammonium sulphites are formed, and finally
ammonia, sulphurous oxide, water, and nitrogen escape. The residue left behind
on cooling is almost pure NH 4 HS0 4 . At the higher temp., the ammonia mol.
and that of sulphur trioxide mutually decompose each other, forming nitrogen,
sulphur dioxide, and water. However, ammonium sulphate at this high temp,
decomposes, so that the hydrosulphate remains as a residue. P. Schweitzer believed
that the hydrosulphate is formed when normal ammonium sulphate is heated,
and at a higher temp, he supposed that the product is diammonium tetrahydro-
trisulphate, (NH 4 ) 2 H 4 (S0 4 ) 3 , while at a rather lower temp., tetrammonium dihydro-
trisulphate, (NH 4 ) 4 H 2 (S0 4 ) 3 , is formed. S. W. Johnson and R. H. Chittenden
appear to regard these salts as mixtures of ammonium hydrosulphate and pyro-
sulphato. H. Schulze found that the pyrosulphatc is formed by a prolonged
)H-;itin<r between 250 and 300". K Janecke obtained 251 for the in.p. of the


hydrosulphate, and 357 for the simultaneous melting and decomposition of the
normal salt under atm. press. Owing to the decomposition of the normal sulphate
in open tubes, it is impossible to determine the m.p. under these conditions. G. Bartha
observed that ammonium sulphate decomposes at 200 in vacuo before volati-
lizing. C. Caspar obtained with an open tube a softening of ammonium sulphate
at 310, a melting at 336-339, and a decomposition at 355 ; and with a closed
tube, a softening at about 360, and a melting at 417-423. The m.p. is probably
much higher than is usually supposed because J. Kendall and M. L. Landon did not
succeed in melting the normal salt in a sealed tube at the b.p. of sulphur about
445 but J. Kendall and A. W. Davidson found that in a closed tube, under an
ammonia press, greater than atmospheric, the salt begins to soften at 490, and
melts at 513 2. It is a unique example in inorganic chemistry, of a sulphate
with a m.p. below that of the corresponding chloride, which melts at 550 under a
press, of approximately 66 atm. Usually the chlorides melt at a lower temp, than
the sulphates.

G. T. Gerlach measured the boiling points of soln. of different cone, with 15'4,
58'0, and 115'3 grms. of salt per 100 grms. of water, the b.p. are 101, 104,
and 108-2 respectively; at 108'2 the solid phase is (NH 4 ) 2 S0 4 . This subject
has also been investigated by S. M. Johnston. C. Matignon and F. Meyer found
the b.p. of a sat. soln. of ammonium sulphate is 108'9, and the soln. contains
3 '922 mols. per 1000 grms. ; and a soln. sat. with both sodium and ammonium
sulphates boils at 111, and contains T125 mols. of the former salt, and 3'175 mols.
of the latter per 1000 grms. of soln. H. Lescceur's value for the maximum vapour
pressure of a sat. soln. is 14'8 mm. at 20. F. M. Raoult found the lowering of the
vap. press, of a 1 per cent. soln. to be - 230 X7*6 ; and G. Tammann, for the lowering
of the vap. press, of soln. of different cone, at different temp. Soln. with 5*18,
43'53, and 79'95 grms. of salt per 100 grms. of water, at 100, lowered the vap.
press. 8'4, 75'9, and 141/0 mm. respectively. Soln. with 13'93 and 40'91 grms. of
salt in 100 grms, of water lowered the vap. press, of water :

32 52 67 76'3 88 93 101

Soln. 13 -93 grms. . I'O 5'2 6'7 9*9 14'5 19'9 24 '3 mm.

Soln. 40-91 grms. . 3 "5 10 "3 2 '9 30 '4 46 "2 58 "0 70 "8 mm.

L. C. de Coppet found that the freezing point of a sat. soln. of the salt, containing
62'2 grms. of salt in 100 grms. of water, is 19'05 ; and, according to F. Guthrie,
when soln. of different cone, are cooled, the solid phase separating at different
temp, is as follows :

Per cent. (NH 4 ) 2 SO 4 . 10 20 40 4J "7 41'9 43'2

Separation at . . -2'6 -6'0 -16 -17 19'0

Solid phase . . Ice Eutectic (NH 4 ) 2 SO 4

The lowering of the f.p. of water by the dissolution of the salt has been investigated
by L. C. de Coppet, F. Riidorff, F. M. Raoult, and by H. C. Jones and his co-workers.
A gram of the'salt in 100 c.c. of water lowers the f.p. 0'276 (L. C. de Coppet), 0'269
(F. Riidorff), and F. M. Raoult gives the lowering of the f.p. of a 1 per cent. soln.
as 0'273, and he gives the mol. lowering of the f.p. as 37'0, when L. C. de Coppet
gives 36'4. H. C. Jones and C. G. Carroll measured the effect of ammonium
sulphate on the f.p. of soln. of hydrogen peroxide and found the depression of the

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