511 



oxide of iron that are capable of forming peculiar acids with the ele- 

 ments of prussic acid ; and the most remarkable of these is sulphur, 

 which makes an acid of a red colour, having always the same pro- 

 perties, though formed in various different ways. The first method 

 by which Mr. Porrett formed this acid, was by boiling together sul- 

 phuret of potash with prussian blue ; but he has also made it by the 

 same sulphuret with prussiate of mercury. Also by heating together 

 sulphuret of potash with animal charcoal, and by sulphate of potash 

 with the same coal. Also by boiling a simple alkaline prussiate with 

 sulphur, or by mixing prussiate of ammonia with hydroguretted sul- 

 phuret of potash. Since one of the properties of this acid is to form 

 an insoluble compound with copper, the author takes advantage of 

 this valuable property for obtaining the acid in a pure state. After 

 decomposing a salt of copper for this purpose, a quantity of sulphuric 

 acid is poured on the precipitate, and the whole submitted to gentle 

 distillation, by which the acid is obtained nearly pure, or may be 

 easily purified. The author examines the salts formed by union of 

 this acid with the several alkalies, earths, and metallic oxides, show- 

 ing that it may be transferred from one to another without change of 

 its properties, and supporting his opinion that it should be regarded 

 as an acid of a peculiar and extremely compound nature. 



For the acids here described, the author invents names by com- 

 bining the initials of three of their constituents, carbon, hydrogen, 

 and azote, which give him the term Chyazic ; and hence he deno- 

 minates the former Ferruretted Chyazic acid, and the latter Sulphu- 

 retted Chyazic acid. By careful analysis of the former, the author 

 found 17'26 oxide of iron in 47'66 of the dry acid; and in 18*4 of 

 the latter he found 1 2 of sulphur. 



In the course of these experiments Mr. Porrett examines and de- 

 scribes the precautions which are necessary in ascertaining the quan- 

 tity of iron present in any solution by the quantity of prussian blue 

 that can be formed : and he also shows the use that may be made of 

 the sulphuretted chyazates as precipitants of copper. He observes, 

 that the precipitate formed in this case contains no water, and con- 

 sists of about 63 protoxide of copper, combined with 37 sulphuretted 

 chyazic acid. 



Some Experiments on the Combustion of the Diamond and other car- 

 bonaceous Substances. By Sir Humphry Davy, LL.D. F.R.S. 

 V.P.R.I. Read June 23, 1814. {Phil. Trans. 1814, p. 557.] 



Notwithstanding the many accurate experiments which have been 

 made and recorded, showing that diamond and carbonaceous sub- 

 stances combine with the same quantity of oxygen, and form the 

 same quantity of carbonic acid, various conjectures have been formed 

 respecting some difference in their chemical composition, which might 

 account for the remarkable difference in various sensible qualities. 

 Messrs. Biot and Arago conjectured, from the great refractive power 

 of the diamond, that hydrogen must be present. Guyton de Morveau 



