26 Mr. Smith and Dr. Brett's Additional Remarks 



are ferrocyanide of potassium and carbonate of potash, and 

 the instrument an iron tube and plug, is so difficult of per- 

 formance that a person may work for six weeks in continual 

 failure? if so, we are totally unable to reconcile such an opi- 

 nion with one or two statements, in very decided language, to 

 be met with near the close of the original memoir, in p. 243 

 of the Transactions : the author there speaks of the production 

 of crystallized siliciuret of iron from the action of heat upon a 

 mixture of ferrocyanide of potassium and cyanide of potassium. 

 "In one operation, "says he, "I procured half an ounce of these 

 little eight-sided crystals, and have worked with glass, porce- 

 lain, black-lead, iron and platinum vessels with equal success." 

 He continues, " This is a difficult process, however, and one 

 must be content to make several trials before a fine product 

 be obtained; but although it is not easy to produce a perfect 

 specimen, it is the simplest thing in the world to satisfy oneself 

 of the change "which is effected ; nay, it is impossible to make 

 cyanide of potassium by the common process mthoiit performing 

 this transformation." And further on we have the following 

 somewhat remarkable statement : — " I have at length come to 

 the conclusion, that the production o^ silicon from paracyano- 

 gen has been performed by every one who has decomposed the 

 ferrocyanide of potassium by heat, in order to procure the cy- 

 anide of the same metal." How comes it, we would ask, if 

 it be the simplest thing in the world to satisfy oneself of the 

 chano^e which is effected, that in all our experiments with 

 ferrocyanide of potassium and carbonate of potash we failed 

 to obtain indications of the presence of silica as the result of 

 a transformative action, but nevertheless obtained abundance 

 of cyanide of potassium ? nay, in one of our experiments, 

 p. 803 of Phil. Mag., where ferrocyanide of potassium was 

 heated alone, we altogether failed in effecting the alleged 

 transformation ; yet Dr. Brown has come to the conclusion, 

 " that the production of silicon from paracyanogen has been 

 performed by every one who has decomposed the ferrocy- 

 anide of potassium by heat." 



But although we have entirely failed in bringing about this 

 transformation, under circumstances, when, according to Dr. 

 Brown, the thing has been done over and over again not only 

 in this but in every country, where cyanide of potassium has 

 been obtained by decomposing the ferrocyanide of potassium by 

 heat ; still he not only effects this alleged conversion, but even, 

 as it appeared to us, proves too much, viz. he gets more silica 

 in one experiment than the carbon, supposing it all to be 

 transformed into silicon and the latter silicified, could yield. In 

 p. 244- of the Transactions we find the following statement : 



