Supplement to a Handbook of Chemical Manipulation - Softcover

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1879 edition. Excerpt: ... stone and sulphuric acid, which, as a rule to which there are few exceptions, is preferable to chloride of calcium for the reasons given at p. 45. Fig. 16. When the substance is to be burned in a current of air or oxygen, or in both, the straight tube (fig. 66) is quite inadmissible, the current of air or gas would be very liable to pass over Bo short a distance too rapidly to allow of complete desiccation. The hydrogen would then be liable to como out too low; and this is one of the worst faults that can occur in an organic analysis. Corks for Combustions.--Wooden corks, if the expression may be permitted, are now very rarely employed in organic analyses. They have been completely superseded by vulcanized india-rubber. They should be selected of several sizes, so as to enable all the combustion-tubing used in the laboratory to be fitted; or, still better, let the combustion-tubing be carefully selected in three sizes only, as directed at p. 356, and then only three sizes of combustioncorks will be required. The above precautions, if followed, will save much trouble, because it is not easy to cut caoutchouc corks in such a manner as to perfectly preserve their form. When it is required to cut them down, the knife must be very sharp and be wetted with solution of caustic soda. The caoutchouc cork may be readily pierced with a cork-borer moistened with solution of caustic soda. It is, perhaps, hardly necessary to remind the student that, if no solution of soda be at hand, the combustion-potash will do as well. Some chemists, instead of an alkaline solution, use oil to facilitate the use of the cork-borer. The caoutchouc combustioncork should be well rubbed with black-lead before being inserted in the combustion-tube; this will prevent it...