A NEW CLASS OF SALTS. 
493 
In the above analysis the proportion of carbon to the iron is higher than obtained 
with the other salts, but the error is usually on this side when chromate of lead, as 
in this instance, is used in the combustion. It will also be seen in a further part of 
the paper, that a carbonaceous impurity, probably an attached cyanide, not separable 
by crystallization, but removed when it is converted into a silver salt, is produced 
when a solution of this salt is kept for some time, and it is possible that a small 
portion may be present in the salt analysed. If we could be assured of the absence 
of all impurity, which it will be afterwards seen that it is difficult to believe from the 
variable composition of this salt, it is obvious that the above analyses might be much 
more simply expressed by the following calculation: — 
2 Iron . . . 
. 56 
Calculated. 
14*03 
2 Barium . . 
. 137 
34*33 
10 Carbon . . 
. 60 
15*03 
6 Hydrogen . 
6 
1*50 
6 Nitrogen 
. 84-) 
35*11 
7 Oxygen . . 
. 56 J 
399 
100*00 
On the first formula the dried salt would be Fcg Cy^g on the 
second FcgCyg NO, Bug-f-dHO. The water lost in the water-bath would in the first 
case correspond to 20equivs., in the latter case to Sequivs. 
Nitroprusside of Silver. 
14. This salt may be prepared by adding nitrate of silver to any of the soluble 
nitroprussides. 
The colour of the salt varies according to its state of preparation, from a fleshy 
white to a pale buff. When dry it has a flesh colour. It is insoluble in water, 
alcohol and nitric acid. Hydrochloric acid decomposes it with the formation of 
nitroprussic acid and chloride of silver. The caustic alkalies decompose it, as they do 
the soluble nitroprussides generally : ammonia dissolves nitroprusside of silver, but it 
soon deposits white crystals, which are apt to be contaminated by oxide of iron. 
These white shining crystals are a compound of the salt with ammonia, and are quickly 
decomposed, even by water alone, but very readily by water acidulated with nitric 
acid. Ammonia is now found in solution and nitroprusside of silver remains. If am- 
monia and nitroprusside of silver be boiled together, a total decomposition takes place. 
The salt was decomposed by sulphuric acid, the silver estimated as a chloride and 
the iron as peroxide. Each salt analysed was prepared at different times. 
I. 14‘788grs. gave 2'749grs. oxide of iron and 9‘925 grs. chloride of silver. 
II. 22‘838grs. gave 4‘220grs. oxide of iron and 15‘180grs. chloride of silver. 
III. 16 675 grs. gave 3T15 grs. oxide of iron and 1T09 grs. chloride of silver. 
IV'. 26*545 grs. gave 4*970 grs. oxide of iron and 17'78 grs. chloride of silver. 
MDCCCXLIX. 3 s 
