184? Prof. Daniell and Dr. Miller on the 



tion of sulphur. This doubtless arose from the secondary 

 action of the sulphuric acid, which was first formed upon the 

 salt with which it was in contact, by which hyposulphurous 

 acid was disengaged and immediately decomposed. The con- 

 stitution of the hyposulphite being (NaO, S^ Og), that of the 

 corresponding sub-oxysulphion would be S^ O35 which if burnt 

 at the zincode would produce S+ SO3. 



5. We now proceeded to apply the method of electrolysis 

 to solve a problem of the same nature as that of the three hy- 

 drates of the phosphoric acid, viz. to determine the exact re- 

 lations of the yellow and redferrocyanides qf' potassium. It is 

 well known that two views have been taken of the constitution 

 of these two salts : the first represents the yellow salt as a 

 Jhrocyanide qf potassium (Kg, Fe Cyg), and the red salt as a 

 subsesquiferrocyanide of potassium K3+2(FeCy3). The 

 second view represents the two salts as compounds of those 

 metals with two distinct radicles, the former denominated,/^r- 

 rocyanogen (Fe Cyg), the latter ferridcyanogen (Feg Cyg). The 

 ferrocyanogen forms a dibasic acid with hydrogen (Hg, 

 Fe Cyg), the salts of which are produced by the substitution 

 of two equivalents of the metals for the two equivalents of hy- 

 drogen ; and the ferridcyanogen forms with hydrogen a tri- 

 basic acid (Hg + Fcg Cyg), with a similar substitution of three 

 equivalents of the metals in their different salts. The real 

 chemical difference, therefore, between the yellow and red fer- 

 rocyanides of potassium, consists in the latter containing half 

 an equivalent less of potassium than the former ; and so with 

 the other salts from the two classes the metallic elements are 

 in the proportion of 1 to 1^. 



Now Mr. Porrett*, the discoverer of the hydroferrocyanic 

 acid (or as he proposed to call it, the ferro-chyazic acid), long 

 since determined that it travelled in the voltaic circuit by the 

 electrolysis of its salts, to the zincode, the iron accompanying 

 the cyanogen in this transfer, contrary to what might previ- 

 ously have been expected. The question which we now pro- 

 posed to determine was, whether J'erridcya?ioge?i as well as fer- 

 rocyanogen would thus constitute a distinct anion under the 

 directing influence of the battery. 



Mr. Smeef has already determined that the subsesquifer- 

 rocyanide of potassium may be formed from the ferrocyanide 

 by the action of the voltaic battery ; and has even proposed 

 the process for obtaining the red salt upon a large scale. He, 

 however, explains the change by the action of nascent oxygen, 

 which he supposes to be evolved at the zincode. He observes, 



* Philosophical Transactions, 1814, p, 629. 

 t Phil. Mag. [S. 3.] vol. xvii. p. 196. 



