556 



ACCOUNT OF A REPETITION OF SEVERAL OF DR SAMUEL BROWN'S 



nitrogen ; and the quantity of the two last was quite at variance with the volumes 

 they should have given, as the succeeding table will shew :- 



We have reserved to the last the account of one remarkable experiment with 

 paracyanogen heated alone in an iron crucible. Dr BKOWX, described in his second 

 communication to the Royal Society, an experiment, in which a quantity of para- 

 cyanogen closely shut up in a Berlin crucible, and kept twenty days in a sand 

 bath, at a temperature of about 800 or 900 F., became converted into silicon.* 

 In imitation of this experiment, we enclosed 10'5 grains of crude paracyano- 

 gen in a Berlin crucible, and kept it at the temperature prescribed for four days. 

 An accident led to the crucible being opened at the end of this time, when the 

 original quantity was found diminished to 1*8 gr. This residue was of a light 

 brown colour, much lighter than paracyanogen, and gritty. It was fused with 

 carbonate of soda, and treated as if for silica, but gave only a trace of insoluble 

 matter. 



This experiment was repeated with a small crucible of malleable iron weigh- 

 ing about 200 grains, containing 18'5 grains of crude paracyanogen. The lid 

 being luted on, and the whole crucible coated with stucco, it was placed over an 

 argand gas flame, and heated continuously for three days. At the end of this 

 period it was opened, and found to contain 4'2 grains of a nut-brown soft powder. 

 3'9 grains of this powder were fused with carbonate of potass, and the product 

 treated with muriatic acid as if it were silicate of potass. 10'4 grains of a reddish- 

 brown powder were obtained, which, when boiled with muriatic acid, washed and 

 ignited, left 8'4 grains of pure white silica. Had the original brown powder been 

 silicon, and by fusion with the carbonate become silica, it should have given 8'11 

 instead of 8'4 grains of the latter. There is thus an excess of 0-29 grain, or 3'6 

 per cent, of silica. In spite of this considerable excess, we believe that few will 

 refuse to acknowledge that the original body was silicon. 



Had we been aware at the time of making this experiment, that our subse- 

 quent trials in other directions would prove so unsatisfactory as they have done, 

 we should have repeated it many times. But, as the object of our inquiry was to 

 ascertain whether carbon was transmutable into silicon or not, we left unrepeated 



* Transactions of Ruyal Society, vol. xv. p 233. 



