Alkalimetry. The method of estimating the strength of alkalis. The processes used are the same as in acidimetry; only that the unknown quantity sought is an alkali, and the test applied is an acid. The test acid is 1 equivalent (40 grains, see No. 81 (Table of Equivalents of Acids)) of sulphuric acid sp. gr. 1.032 at 60° Fahr. inserted in an acidimeter (see No. 82 (Acidimeter)) and made up with distilled water to 100 acidimetric divisions.

84. To find the strength of an Alkali

84. To find the strength of an Alkali. Place 100 grains of the alkali in a tube, and agitate it with about 1/2 ounce hot water. When settled, pour off' the clear into a vessel for trial, Repeat this process until nothing soluble remains in the test tube, shown by the last washing not affecting the color of turmeric paper. Care must be taken not to waste the smallest portion of the liquid, as it would render the results inaccurate.

Next, exactly neutralize the alkaline solution by adding sufficient of the test acid drop by drop. If the saturation is complete, it will neither turn litmus paper red, nor turmeric paper brown. (See No. 78.) The weight of alkali tested, bears the same relation to its equivalent weight (see No. 80 (Table of Equivalents of Alkalis)), that the acidimetric divisions of acid used, do to the percentage of alkali sought.

Thus:- If we test 100 grains of potash and find it requires 35 acidimetric divisions of test acid to saturate it, wo refer to table No. 80, and find that the equivalent of pure potash is 47 grains. Then 100 : 47 :: 35 :16.45.

That is, the sample of potash under examination contains nearly 161/2 per cent, of pure potash. (See No. 587 (To Find the Percentage of Carbonated Alkali in a Caustic Soda or Pot-ash).)