. Public health laboratory work, including methods employed in bacteriological research, with special reference to the examination of air, water and food contributed . o o 1 Fig. 41.âBurner with fittings used for estimating sulphur compounds. washings are added to and mixed with the contents ofthe beaker. Fresh pieces of sesqui-carbonate of am-monia are to be used for each test. Slight excess ofhydrochloric acid, followed by an excess of a solution ofthe chloride of barium, are next added to the whole-which is then well boiled for five minutes. The precipitate of sulphate of baryta which has f
. Public health laboratory work, including methods employed in bacteriological research, with special reference to the examination of air, water and food contributed . o o 1 Fig. 41.âBurner with fittings used for estimating sulphur compounds. washings are added to and mixed with the contents ofthe beaker. Fresh pieces of sesqui-carbonate of am-monia are to be used for each test. Slight excess ofhydrochloric acid, followed by an excess of a solution ofthe chloride of barium, are next added to the whole-which is then well boiled for five minutes. The precipitate of sulphate of baryta which has formed must be col-lected on a Swedish filter paper, and then several quan-tities of hot distilled water passed through the filterâso that it may be thoroughly freed of any baric chlorideand ammonium chloride remaining behind with the 250 LABORATORY WORK. baric sulphate. This washing is repeated, there-fore, until a drop of a solution of silver nitrate, addedto the filtrate in a test-tube, gives no cloudiness. Thefilter paper, with its contained baric sulphate, has thento be dried in the water oven; and afterwards folded up. Fig. 42.âComplete apparatus for estimating the sulphur compounds in coal gas. and placed within a weighed platinum dish, which isthen gradually heated to redness, and retained thusuntil the filter paper has burnt off (, no dark specks,&c., remain). Then the platinum dish is allowed tocool in a desiccator over strong sulphuric acid, and ANALYSIS OF COAL GAS. 25I subsequently weighed. The excess of this weight overthat of the empty dish is due to baric sulphate. Now the atomic weight of barium = 137. sulphur = = 16. .*. the combining weight of the compound (BaS04) =233, of which S = 32. .*. the sulphur forms -^% ofBaSO^, , 0-137. .*. Supposing 8-6 grains of baric sulphate are foundin 10 cubic feet of gas, then 8*6 x 0*137 will represent1-178 grains of sulphur in 10 cubic feet, or 11-78 grainsin 100 cubic feet. The number is to be corrected
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