. Chemistry: general, medical, and pharmaceutical, including the chemistry of the U. S. Pharmacopia. A manual on the general principles of the science, and their applications in medicine and pharmacy. cid, is drawn over it; when the color of the chromatechanges to brown, the heat can be withdrawn and the extremityof the tube farthest from the drying-apparatus closed, so thatthe air in passing into the tube on cooling may be quite dry ;when cool, the drying-tube is removed, and the extremitysecurely corked; the lead chromate is then ready for directtransference to the combustion-tube. The gener
. Chemistry: general, medical, and pharmaceutical, including the chemistry of the U. S. Pharmacopia. A manual on the general principles of the science, and their applications in medicine and pharmacy. cid, is drawn over it; when the color of the chromatechanges to brown, the heat can be withdrawn and the extremityof the tube farthest from the drying-apparatus closed, so thatthe air in passing into the tube on cooling may be quite dry ;when cool, the drying-tube is removed, and the extremitysecurely corked; the lead chromate is then ready for directtransference to the combustion-tube. The general manipulations for substances containing nitrogenresemble the foregoing so far as the use of a combustion-tubeand furnace and collection of the ammoniacal gas are combustion-tube must be quilled at one end and about athird of a metre long. The soda-lime is made by slakingquicklime with a solution of soda of such a strength that about2 parts of quicklime shall be mixed with 1 of sodium hydrate,drying the product, heating to bright redness, and finely pow-dering ; it should be preserved in a well-closed bottle. Someof the soda-lime is introduced into the tube, then layers of sub-. 692 GRAVIMETRIC QUANTITATIVE ANALYSIS. stance and soda-lime, mixture effected by a wire, a good layerof soda-lime added, and a plug of asbestos. Bulbs (Fig. 88), known as those of Will andFig. 88. Varrentrapp (the originators of the method), containing hydro-chloric acid of about 25 percent., are then fitted by a cork,and the tube heated in the fur-nace—to a not too bright redheat, or some of the producedammonia eras may be decom- Nitrogen-bulbs. , ,,T9 J posed. When gas ceases to passand combustion is considered to be quite complete, the tube isallowed to cool somewhat, the quill is then broken, and aspira-tion continued slowly until all ammoniacal gas may be con-sidered to have been absorbed by the acid. The bulbs are dis-connected, their contents and rinsings poured into a small dis
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