Page:Experimental researches in chemistry and.djvu/194

1826 a tube, it became charred, yielding much ammonia. It resembles albumen more than any other substance, and is the source of the nitrogen or ammonia obtained by the distillation of common caoutchouc.

The brown aqueous solution (a) became frothy on agitation; alkali rendered it of a deep yellow colour, and produced a putrescent odour, similar to that evolved by alkali or quick -lime from white of egg or blood. It was remarkably distinguished by the deep-green colour it produced with persalts of iron, especially when a little alkali was present, and the dense yellow precipitates it formed with muriate of zinc and nitrate of lead; indeed, precipitates were produced in solutions of most of the metals by it. The colour produced with iron does not seem to be a precipitate.

With the hope of obtaining something peculiar from this solution, a quantity of it was precipitated by nitrite of lead; a colourless solution and a yellowish-green precipitate were obtained. The latter, being well washed, was next diffused through water, and sulphuretted hydrogen passed through it; by filtration a deep brown solid was obtained and a yellowish solution. The precipitate when washed and dried was brittle and hard; on platina-foil it at first burnt with flame, swelling much, and giving out odour of ammonia like animal matter; after that sulphurous acid burnt oft; and ultimately lead and oxide of lead remained; hence it was a combination of sulphuret of lead, and a highly azoted substance. Heated in a tube, it gave out much ammonia; digested in alcohol, scarcely a trace of matter was removed.

The sulphuretted hydrogen solution, being boiled and eva* porated, left a yellow varnish-like substance, not deliquescent, soluble in water, acid to taste and to litmus, the acid not being sulphuric: it rendered per sulphate of iron green, precipitated nitrate of lead, and gave no ammonia by heat.

The concentrated solution (a) acted upon by alcohol, had an insoluble matter thrown down, which being separated and well washed with alcohol, was afterwards treated with water, a deep brown aqueous solution (b) was obtained, and a small insoluble portion left; this was almost black when dried, tasteless, brittle, burning with difficulty, and when heated in a tube giving much ammonia.