304 _ Analyses of Books. [APRIn, 
the air, nor redden litmus paper. When kept, it acquires a red 
colour, and is partly converted into purpurate of ammonia. 
Its constituents, according to the analysis of Dr. Prout, are 
as follows : 
Hydrogen 2 atoms.......++. = 0:25 or per cent. 4°54 
SUL OD. 2, AUOINS a's vis a a aye oye LDU reek ambemetie cf oo, 
WRYSCN 2 ALOUIS, om oisse.95.0 pide ZU npn Mesieeteey OU 
BARS CAR a ater ns aa ay fs Memipessbee secs) Wot | 
——— 
5-50 99-98 
But as his analysis was limited by the small quantity of acid in 
his possession, he seems to place but little confidence in the 
accuracy of the preceding numbers. 
The purpurate of ammonia crystallizes in four-sided prisms, 
which, when viewed by transmitted light, have a deep garnet 
red colour. But by reflected light, the two broadest faces appear 
of a brilliant green, while the other two faces appear of dull 
reddish brown colour. Itis soluble in about 1500 parts of water, 
and the solution has a deep carmine red colour. The solution 
has a slightly sweetish taste ; but no smell. 
The other purpurates were obtained by double decomposition 
from purpurate of ammonia. 
Purpurates of potash and soda are red. They may be obtained 
in crystals, which resemble in colour purpurate of ammonia. 
The latter is much more insoluble in water than the former. 
Purpurates of lime, strontian, barytes, are green-coloured 
powders, which form reddish purple solutions in boiling water. 
Purpurate of magnesia is a very soluble salt of a most beauti- 
ful purple. 
Purpurate of ammonia does not throw down gold, platinum, 
copper, lead, nickel, or iron, from their solutions in acids. 
Silver is thrown down deep purple; mercury, reddish purple ; 
zinc, golden yellow; tin, pearl white; and cobalt, reddish. 
X. Astronomical Observations and Experiments, selected for 
the Purpose of ascertaining the relative Distances of Clusters of 
Stars, and of investigating how far the Power of our Telescopes 
may be expected to reach into Space when directed to ambiguous 
celestial Objects. By Sir William Herschel, Knt. Guelp. LL.D. 
F.R.S.—As it would be scarcely possible to render this curious 
but rather intricate subject intelligible to our readers without 
devoting to it a greater portion of space than we can well spare, 
Iam under the necessity of referrmg those who wish to study 
the subject to the paper itself. . 
_ XI. On the Structure of the poisonous Fangs of Serpents. By 
Thomas Smith, Esq. F.R.S.—When the poisonous fangs of 
serpents are attentively examined, a slit, or sutor, may be 
observed extendine along the convex side from the foramen at, 
the base to the aperture near the point. This is the consequence 
