214 Mr JOHNSTON on the Combination of Chlorine 



Now from the way in which the salt is formed, it is evident 

 that no such change of composition can have taken place. For 

 we have here the cyanogen ( 6 atoms) and iron '(=. 2 atoms) 

 of 2 atoms of the common prussiate *, contained in each atom 

 of the new salt in combination with only 3 atoms of potassium ; 

 so that to form it we have only to deprive the common prussiate 

 of its water, and of half an atom of potash. Upon what principle 

 of affinity, then, can the action of chlorine produce this separa- 

 tion ; and, if produced, what becomes of the potash, since the 

 liquor may be made to crystallize to the last drop ? It cannot 

 be in the green powder, which, during concentration, is often 

 deposited ; for its quantity is variable, and it is plainly the result 

 of decomposition. The ratio of the atoms, therefore, must be 

 different from what he states it to be, and there is no reason why 

 it should not be the same as in the original salt. 



Again, this statement throws no light on the action of the 

 chlorine in forming the new salt. This gas must act in one of 



* There are various ways of stating the composition of this salt. According to 

 BERZELIUS, who considers the prussiates as compounds of 1 atom of cyanide of iron 

 f 2 atoms cyanide of another metal, it consists of 



Potassium 2 atoms, =r 10-0 ~\ 



Iron i = Jl > = 26>625 



Cyanogen 3 ... = 9'75 ( 

 Water 3 ... = 3-375 ) 



2. According to Dr THOMSON, it is composed of 



2 atoms potash, = 12-0 ~l 



1 ... protoxide of iron, = 4-5 > 26-625 



3 ... hydrocyanic acid, = 10-125 J 



3. While Mr PHILLIPS states it thus : 



1 atom ferro-cyanic acid, = 14-625 ) 



i A A f "o'biso 



2 ... potash, =12-0 J 



BERZELIUS considering the water present to be merely that of crystallization, and 

 Mr PHILLIPS viewing the iron as a constituent of the acid, coinciding in this point 

 with Mr POERETT. 



