On Chemical JVomenchiure. 271 



ical reader a series of names, as for instance haloargentic, halocu- 

 pric, halostannic, halopalladic. 



I consider prussian blue as a cyanoferrite of the cyanobase of iron, 

 or briefly a cyanoferrite of iron. The diversity of properties which 

 enables two cyanides of iron to exist in combination in this cyanofer- 

 rite, one as an acid, the other as a base, is one among many other 

 instances in which compounds constituted of the same elements in 

 the same ratio, have different properties, and are said in consequence 

 to be isomeric, or to afford cases of isomerism. 



The salt designated by Berzelius as the " cyanure ferroso-potass- 

 ique,"*^ is the well known test for iron heretofore called ferroprussiate 

 of potassa ; under the idea that it consisted of prussic acid, iron, and 

 potassa. As the prussic acid was viewed at the same time as a com- 

 pound of liydrogen and cyanogen, the ferroprussic acid was consid- 

 ered as a compound of cyanogen, hydrogen, and iron. According 

 to Berzelius, the supposed /erroprwssia^e is a compound of a "pro- 

 tocyanure" of iron, and a "cyanure oi potassium ;" each being a sim- 

 ple haloid salt, and the aggregate a double " cyanure.''^ Agreeably 

 to my nomenclature, the "protocyanure " of iron is considered as cy- 

 anoferrous acid, and the " cyanure'''' of potassium as a cyanobase ; 

 the aggregate being a cyanoferrite of the cyanobase of potassium, but 

 designated briefly as a cyanoferrite of potassium. 



I infer that the "ferroprussic'^ acid is analogous in constitution to 

 the triple compound of fluorine, silicon and hydrogen, improperly call- 

 ed hydrofluosilicic acid ; and that, consistently with the hypothetical 

 views under which the latter received its name, the former should be 

 called hydrocyanoferric acid. Even admitting the correctness of the 

 hypothetical impression, to which I have alluded, agreeably to which 

 such compounds are acids with a double radical, I urged that the ap- 

 pellations of such compounds should be so altered as to give prece- 

 dency to the electro-negative ingredient. Hence the one would be 

 called cyanohydroferric acid ; and the other, fluohydrosilicic acid. 

 But in my letter to Prof. Silliman, already cited, I advanced a new 

 hypothesis respecting the constitution of the fluohydrosilicic, and 

 fluohydroboric acids. I suggested that they should be considered as 

 compounds in which the fluorides of silicon or boron acted as acids, 

 the fluoride of hydrogen as a base. Consistently with that doctrine, I 

 would consider the protocyanide (or "cyanure'") of iron in the alleged 

 ferroprussic acid, as acting as cyanoferrous acid, the cyanide of hy- 

 drogen {prussic acid) as a cyanobase forming, by their union, a cya- 

 noferrite of hydrogen. 



