204 Progress of Foreign Science. 
was 89° 35’. The axes of the octohedron are consequently in 
the ratio of 1 to 1.404. Ifthe edge B makes with B, situated 
on the other side of the axis, an angle of 109° 28’, this ratio is 
as 1: /2. 
Angles of the Crystals. 
BR ePh = 89° 30 5 
Poe Re 90" 25's 
Pe 9 19? AG 
t.2-P += 185°. 124. 
Of the Arseniate and Phosphate of Ammonia. 
We obtain these salts by adding ammonia to concentrated 
arsenic or phosphoric acid, till a precipitate be formed. On 
heating the liquid, the precipitate is dissolved. If we then 
leave the solution to itself, preventing too much of the ammonia 
from flying off, there are formed, after a certain time, large and 
beautiful crystals of neutral salt. It happens sometimes, however, 
that crystals fall down during the cooling of the solution, 
which are a subsalt with basis of ammonia, which were not 
examined because they change instantly on exposure to the air. 
The crystals of the neutral salts are decomposed in the air. 
They are more soluble in water than the crystals of the bin- 
arseniate and bi-phosphate of ammonia. ‘The solution of these 
crystals precipitates the muriate of barytes, so that the liquor 
exhibits a neutral re-action. On analyzing the precipitated 
barytic salts, they were found to be neutral. Hence the ammo- 
niacal arseniate and phosphate were neutral also. Without 
paying attention to the crystalline form, it is impossible to make 
an analysis of the salts with base of ammonia, both acid and 
neutral ; for on making a solution crystallize, we always obtain 
a mixture of the acid and neutral salt. By processes analogous 
to those previously described, the acid, and the-sum of the 
ammonia and water contained in the salt were determined. 
100 parts of arsenic acid combine with 29.804’parts of am- 
monia, and consequently with 24.345 of water, to form the 
neutral salt. It contains 1} proportion of water, and consists, 
by the atomic determination of Berzelius, of 
Arsenic acid . . 65.28 
Ammonia. . . 1044€100 
Water 5 op. 15.28 
100 parts of phosphoric acid, combine in forming the neutral 
phosphate of ammonia, with 48.06 parts of ammonia, and con- 
sequently, with 35.675 parts of water. The neutral phosphate 
of ammonia contains therefore 14 proportion water, and con- 
sists, according to Berzelius, of 
