343 



his Inaugural Dissertation in 1839, as carburets of the metal. 

 (See Trans. Brit. Assoc. 1839, vol. ix.) Experiments were added 

 under the present section, which satisfied the author that every 

 conceivable source of silicon, except from the paracyanogen, was 

 provided against by the manner in which the experiments of con- 

 version were performed. Among other facts thus elicited, it ap- 

 peared, that, by successive operations in the same vessel, a greater 

 weight of disiliciuret of iron might be obtained than the weight of 



•'•essel itself. 



5. Silicic acid may be obtained by a direct process from the 

 paracyanide of iron. The conversion thus accomplished might 

 appear, as the author conceived, more satisfactory to most per- 

 sons, than any of the previous operations, on account of the large 

 scale on which the experiments were performed. When paracy- 

 anide of iron was mixed with four times its weight of carbonate of 

 potash, and ignited in a shut crucible of hammered iron for four 

 hours at a full white heat, a rose-red saline product was formed, 

 from which a transparent solution was obtained with water ; and 

 when this was supersaturated by hydrochloric acid, a bulky pre- 

 cipitate was thrown down, which, when purified from adhering 

 metallic oxide by fusion with carbonate of potash, solution of the 

 product in water, neutralization with hydrochloric acid, evapora- 

 tion, desiccation, and ignition, and elutriation with water to 

 remove chloride of potassium, — presented all the distinctive cha- 

 racters, physical as well as chemical, of silicic acid. Five grains 

 of paracyanide of iron thus gave 3.04 of silicic acid ; and 30 

 grains of ferrocyanide of potassium, similarly treated, gave 5.4 

 grains of silicic acid. The iron crucible used in these operations 

 did not yield a particle of silicic acid when heated to a white heat 

 with pure carbonate of potash, — the same salt employed in the 

 preceding cases of conversion. A large crucible was worked 

 seven successive times with 9334 grains in all of ferrocyanide of 

 potassium ; and 1240 grains of silicic acid were produced. 



The author added that, in the course of several of these opera- 

 tions, more especially those of the last section, he found the iron 

 to undergo conversion as well as the carbon ; and in a subsequent 

 paper he proposes to state in detail the facts which lead him to the 

 conclusion that this metal is a variety of the same elementary 

 form with rhodium. 



