306 . ,. • Professor Berzeliiis on [ A Pii i l, 



lie state, and that it is a constituent part of this acid, are not 

 decisive. 



,[ To verify this idea by direct experiment, I put 23*16 grs. of 

 effloresced ferruginous prussiate of potash into a small appa- 

 ratus, made by the lamp, and so disposed that a current of 

 sulphuretted hydrogen gas might be passed over the salt. 

 At the common temperatures it was not at all altered. I then 

 heated it by a spirit-lamp, slowly increasing the temperature 

 until the mass fused. Ihe sulphuretted hydrogen gas was 

 passed over it until the mass became cold. I had supposed that 

 ihe sulphuretted hydrogen would decompose the protoxide of 

 iron, producing hydrocyanic acid, water, and sulphuret of iron; 

 but no trace of water appeared. The sulphuretted hydrogen, 

 both at entering into, »nd leaving the apparatus, was passed 

 over fused muriate of lime, in order that the water, that might be 

 jformed during the operation, might be correctly weighed. At 

 Ihe end of the experiment, the prussiate had gained 11*6 per 

 -<:ent. in weight, and the muriate of lime 21 hundredths of the 

 '^weight of the prussiate. But on heating the muriate of lime, to 

 ^ee if what it had absorbed was water, it gave off only hydro- 

 jsulphuret of ammonia, and pure ammonia, with traces of mois- 

 ture. No disoxidation of the protoxide of iron, therefore, had 

 taken place, and the experiment appeared to confirm Mr. 

 Porrett's idea. A great part of the salt had been converted 

 into sulphuretted hydrocyanate of potash ; a small portion 

 jemained undecomposed, and some sulphuret of iron was 

 formed. 



I next endeavoured to decompose the anhydrous prussiate by 

 •distiUing it with fused boracic acid, to ascertain if, during this 

 operation, borate of iron would be formed ; but the mass swelled 

 up greatly during the process, and passed out of .the retort, so 

 that its neck was soon stopped up by it. The disengaged gas was 

 cyanogen, mixed with a little hydrocyanic acid. After the cal- 

 cined mixture had been dissolved in water, a brownish mass 

 jemained, insoluble in muriatic acid, which, exposed to heat, 

 gave borate of iron ; whence it appeared that the boracic acid 

 liad been in part decomposed. 



Thus the nonoxidated state of the iron seemed proved by these 

 experiments. When I calculated the above-mentioned analyses, 

 the result appeared to coincide with the following composition : 

 one atom of metallic iron, two atoms of the oxide of the other 

 Teases, two atoms of cyanogen, and three atoms of prussic acid. 

 It thus remained to determine by combustion, if that be the true 

 state of the matter. 



In consequence, I burned, in a glass tube surrounded by ano- 

 ther of tin-plate, a mixture of 7*72 grs. of anhydrous ferrugi- 

 nous prussiate of potash, and 231*66 grs. of pure oxide of copper, 

 prepared by the decomposition of nitrate of copper by heat. 

 . The mixture wa§ made in a porphyry naortar, heated to above 



