o?i the alleged Conversion of Carbon into Silicon. 29 



or this substance prepared by heat from bicyanide of mer- 

 cury ? which, according to Dr. Brown, contains " a third of 

 its own weight of condensed cyanogen," is " hygrometric," 

 which, " when thus prepared, may have suffered the loss of 

 some of its nitrogen," may contain metalUc mercury, " half 

 charred cyanide of mercury, paracyanide of mercury," and 

 for aught we know, a variety of other compounds ; besides, 

 at the temperature to which this so-called hydrate of para- 

 cyanogen was exposed by us in our various experiments, the 

 water must have been driven off' before any action could have 

 taken place between it and the carbonate of potash, &c. ; and 

 this we find to be the case, for when the paracyanogen we 

 principally employed is exposed to heat, water is first given 

 off' in small quantities, and then cyanogen. To put this be- 

 yond dispute, 3 grs. of this paracyanogen were heated over a 

 spirit-lamp until no aqueous vapour was evolved, but always 

 kept considerably below redness ; it was then transferred to a 

 small tube apparatus of German glass, well cleaned and warm- 

 ed, and containing "27 cub. inch of atmospheric air, in which 

 6 grs. of potassium were placed ; on the application of heat, 

 vivid ignition ensued in the tube, and air was driven over, 

 which, collected over mercury, when examined for hydrogen, 

 afforded no indications of the presence of that gas ; nor was 

 the apparatus itself in the least perceptible degree clouded 

 by aqueous vapour; cyanide of potassium was formed. — 

 (J. D. S.) 



Now as 1 gr. of water would yield about 5 cubic inches of 

 hydrogen, and as there was no increase in the volume of air 

 contained in the tube, nor moisture deposited, we think we 

 are justified in contending, that at the temperatures at which 

 the transformative action is alleged to take place, the para- 

 cyanogen used by us was at least as pure paracyanogen as 

 that employed by Dr. Brown. In its general properties it 

 fully agrees with the description of the properties of para- 

 cyanogen in pp. 166-7 of the Transactions. We therefore 

 deny the right of Dr. Brown to avoid all notice of our nu- 

 merous satisfactory and decisive experiments made with this 

 substance, because it was " not prepared in exactly the same 

 way " as that which he used, asserting that our paracyanogen 

 was as truly paracyanogen as any employed by him, even ac- 

 cording to his own showing. 



He then proceeds to consider the experiment made with 

 paracyanogen obtained from bicyanide of mercury, remarking, 

 that he has no " sufficient evidence" to show that the pre- 

 liminary process was rightly performed ; yet the sole difference 

 in this process from those described by him, was the substitu- 



