Cooley's cyclopaedia of practical receipts and collateral information in the arts, manufactures, professions, and trades including medicine, pharmacy, hygiene, and domestic economy : designed as a comprehensive supplement to the Pharmacopoeia and general book of reference for the manufacturer, tradesman, amateur, and heads of families . sen the frothing. ObJec.,precau., Sfc. Ob-jections have been raisedto this mode of testing,from the great frothingwhich often occurs with organic mixtures, andfrom antimony and imperfectly charred organicmatter also forming crusts somewhat resem- 1 Animal tissu
Cooley's cyclopaedia of practical receipts and collateral information in the arts, manufactures, professions, and trades including medicine, pharmacy, hygiene, and domestic economy : designed as a comprehensive supplement to the Pharmacopoeia and general book of reference for the manufacturer, tradesman, amateur, and heads of families . sen the frothing. ObJec.,precau., Sfc. Ob-jections have been raisedto this mode of testing,from the great frothingwhich often occurs with organic mixtures, andfrom antimony and imperfectly charred organicmatter also forming crusts somewhat resem- 1 Animal tissues and liquids containing organic matterare best prepared for testing for arsenic by Marshs test,in the following manner proposed by Odling :—Tlie tissue,or the residue obtained by the evaporation of a liquid overa water-bath, is to be thoroughly dried at a temperatureOf about 212° F., then ground to powder or cut up intosmall pieces, next drenched with the strongest hydro-chloric acid and allowed to stand twenty- four hours in awarm place, and finally distilled. The distillate will con-tain arsenic(if it existed in the material underexamination)comparatively free from organic matter, and is, therefore,in a fit state to be introduced into Marshs apparatus, asthe organic matter, which ia the cause of frothing, hasbeen bling, to the inexperienced eye, those producedby arsenic. But these objections are invalid,because there are easy means of purifying theliquid before testing it, and of discriminatingbetween true arsenical spots or deposits andfalse ones. Another objection is, that bothzinc and sulphuric acid sometimes containarsenic; but to obviate this difficulty, we haveonly to use them when perfectly pure; and totest them by means of the apparatus beforepouring the suspected liquid into it. Indeed,these objections apply with equal force to allthose tests which depend on the production ofnascent hydrogen. The precaution necessary tosuccess, and to reliable results,
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