160 Analif sin of Scientific Books. 



ing. This reminds us of the late Mr. Heron, a translator of 

 Fourcroy, who, meeting' the expression, " precipite per se," 

 imagined that the two last words were one, (perse) and produced 

 under mercury, a Persian precipitate, to the no small astonish- 

 ment of the English chemists. 



The sulpho-chyazic acid of Mr. Porrett, which the Doctor, 

 in his 5th edition, by atomic juggling, converted into " a com- 

 pound of 1 atom of cyanogen + 3 atoms sulphur," in defiance 

 of Mr. Porrett's experiments, has now become a compound of 

 2 atoms sulphur -f- 1 atom hydrocyanic acid. We have no pa- 

 tience to follow him through these atomic tortuosities. 



The Doctor's dilemma between hypothesis and experiment on 

 the feriochyazic, or ferroprussic acid, is quite comical. '' I con- 

 sider it as proved that the acid is composed as follows : 



2 atoms carbon = 1 .500 



1 atom azote 1.750 



1 atom hydrogen 0.125 



i atom iron 1.750 



5.125 



" But as the equivalent number 5.125 cannot be reconciled 

 to the composition of the salt, I see no other alternative than 

 to suppose that the iron, in reality, amounts to a whole atom, 

 although I have only been able to obtain half an atom. On 

 that supposition, ferro-chyazic acid must be composed as 

 follows : 



2 atoms carbon = 1 .500 



1 atom azote 1.750 



1 atom hydrogen 0.125 



1 atom iron 3.500 



6.875 

 " This would make the weight of the equivalent number for 

 the acid 6.875. I am disposed to suspect that it will ultimately 

 turn out to be 6 75, which would be the weight of an atom of 

 cyanogen, united to an atom of iron*." What are we to be- 

 lieve, amid these threefold contradictions ? and what becomes 

 of his " considering it as proved" that the first proportion is 

 correct? His first atomic proportion gives 34.186 per cent. 

 of iron ; his second, 50.9 in the same acid. Can his analytical 

 methods not furnish him a better approximation than these 

 two numbers? Under ferrochyazate of potash, he says not 

 one word on its composition, though it is, undoubtedly, the 

 most interesting salt to the practical chemist in his whole 

 system. The ferrochyazates, too, are all misplaced ; they are 

 in no sense frimarij compounds. 



♦ System, II. Ml 



