1821.] the Composition of Frussiates, 303 



and digested them together, till all the iron was precipitated in 

 the state of red oxide. The excess of oxide of mercury was then 

 separated by strong calcination : 30*88 grs. of the prussiate in 

 question gave, in this manner, 6*42 grs. of oxide of iron. The 

 mean result of these analytical experiments is, therefore, as 

 follows : 



Oxygen. 



Potash 44-62 contains 7-58 .... 2 



Protoxide of iron 16*64 3*79 .... 1 



Water 12*70 11*30 .... 3 



Loss 26*04 



100*00 



It follows from this, that the potash contains twice, and the 

 water three times as much oxygen as the iron, in the state of 

 protoxide. The loss is nearly equal to the weight of four atoms 

 of hydrocyanic acid ; but the supposition that the salt should 

 contain this number of atoms is the less probable, because in 

 that case, the weakest base, the protoxide of iron, must contain, 

 relatively to its ordinary capacity of saturation, twice as much 

 acid as the potash, the stronger base. 



(B.) Salt with Base of Barytes. 

 This salt was obtained by digesting prussian blue with hydrate 

 of barytes and water. The undissolved portion was treated with 

 boiling water as long as it dissolved any thing, and the solutions 

 were evaporated to a very small quantity. During the evapora- 

 tion, the barytic salt crystallized irregularly, and it was neces- 

 sary to redissolve it in boiling water, from which it separated on 

 cooling, in the form of small yellowish crystals. It suffered no 

 change at common temperatures, but at 104° Fahr. it began to 

 effloresce. The crystals do not fall to powder, but only lose 

 their transparency, and assume a milky appearance: 30*88 grs. 

 of this salt lost, in this manner, in different experiments, from 

 5*09 to 5*12 grs. of water. I placed the remaining 25*76 on a 

 small porcelain capsule, which I heated red by the flame of a 

 spirit-lamp with a double current {et ct double coiiraiit), and con- 

 tinued the heat till all the combustible matter was burnt away : 

 the residuum was a mixture of barytes and red oxide of iron, weigh- 

 ing 24*63 grs. Dissolved in muriatic acid, and then precipitated 

 by sulphuric acid, it gave 24*13 grs. of sulphate of barytes. 

 After this was separated, I added ammonia in excess to the 

 liquid, which threw down 4*09 grs. of red oxide of iron. Accord- 

 ing to this experiment, the barytic salt contains : 



Oxygen. 



Barytes 51*273 containing 5*38 .... 2 



Protoxide of iron. . 11*865 2*70 .... I 



Water 16*560 14-72 .... 6^ 



Loss 20*302 



100-000 



