Analysis of several bituminous minerals
Journal of the Franklin Institute
We then had recourse to Marsh~s apparatu% and as the scum prevented a continuous flow of the gas, we allowed it to accumulate in the short branch of the tube~ and opened the cock only when the froth had disappeared. Thiswas expedited by moving a piece of ignited coal round the tub% bent at right angles about ti~ree inches above the cock to which it was adapted. This tube was heated to redness in the middle of its horizontal part. • A quantity of arsenic, quite considerable, was here deposited;
... as here deposited; and the extremities of the tube being sealed by a lamp, the specimen was easily preserved. This last method o[ decomposing arsenical hydrogen is unquestionably the best, for no portion of the gas is lost, and by continuing the operation, we obtain within a short space almost the whole of the arsenic contained in the substance to be analysed; and if we are careful as soon as the operation is ore% to close the end of the tub% the arsenic preserves indefinitely its metallic brilliancy when exposed to the air. We were given also some fecal matters to examine, which we had only to boil tbr a few moments in distilled water~ to obtain, by the above process, results which were very satisfactory. I ought to mention, that we rigorously examined the purity of the sul, phuric acid and the zinc employed in the investigation, and after each operation we changed the zin% lest some arsenic might be deposited on it. My only object in this note is to recommend the process of Marsh as the most eligible for its simplicity, ease, and the certainty of its results. Our application of it is the first, 1 belier% in so grave a case of medical jurisprudence.