110 Dr. Thomson on [August, 



uents which I wished to ascertain. I usually left the caustic 

 potash in contact with the gas for 24 hours. 



Five grains of the triple prussiate when decomposed in this 

 way gave out 7*625 cubic inches of gas at the temperature of 

 60°, and under a pressure of 30 inches of mercury : 5-205 cubic 

 inches of this gas were absorbed by potash, and were of course 

 carbonic acid gas. The remaining 2*420 cubic inches were 

 azotic gas. The muriate of lime had increased in weight 2*2 

 grains. Now if 100 grains of the salt contain 13 grains of 

 water, it follows that five grains contain 0*65 grain ; so that 

 1/55 grain of water had been formed by the union of the hydro 

 gen of the salt with the oxygen of the peroxide. Hence five 

 grains of triple prussiate contain a quantity of hydrogen equal 

 to i of T55 grain to 0*1722 grain. From this analysis it follows 

 that the acid in the triple salt (not reckoning the iron) is com- 

 posed of 



Carbon 0*6579 42*51 



Azote 0*7175 46*37 



Hydrogen 0*1722 11*12 



100*00 



* 



From Gay-Lussac's analysis of cyanogen, I expected that the 

 carbonic acid would have been exactly double the bulk of the 

 azotic gas ; but it always exceeded that amount in all my expe- 

 riments (10 in number) by about the third part of a cubic inch. 

 My glass jars were graduated to tenths of a cubic inch ; and each 

 division was of such a size that I could very well appreciate by 

 the eye a quantity not exceeding the fiftieth part of a cubic inch. 

 The difference cannot then be ascribed to errors in the measure- 

 ment ; I do not know to what cause we are to suppose it owing. 



From the preceding analysis, we see that the triple prussiate 

 of potash is composed as follows : 



Acid £ Irou 15 '° I 45*90 



I Gaseous matter 30*9 y 



Potash 41*64 



Water 13*00 



100*54 



The small excess would vanish if we were to estimate the 

 iron at only 14*22 ; but I am rather disposed to ascribe it to 

 errors in the analysis. It may probably be equally divided 

 among all the ingredients. 



As the salt in question bears all the characters of a neutral 

 ^alt, it is reasonable to infer that it is a compound of one atom 

 acid and one atom base ; and as an atom of potash weighs six, 

 it follows that an atom of Mr. Porrett's ferrureted chyazic acid 



4 



