74. To find the strength of Acetic Acid by Saturation without an Acidimeter

74.    To find the strength of Acetic Acid by Saturation without an Acidimeter. The foregoing method can also be applied to test by weight, instead of by an acidimeter; 1000 grains of the test liquid are used in testing 100 grains of acid. Every grain of the test liquid necessary to produce saturation indicates j\, grain of dry acid, and every ten grains are equal to 1 per cent. Schuster's alkalimeter is a convenient instrument for this process. (See No. 82 (Acidimeter).) 1000 grains of the test liquid are introduced into the alkalimeter, and the whole weighed; the weight of the bottle and solution, after using such portion of its contents as is required for testing, deducted from the previous weight of the whole, gives the exact quantity in grains of the solution consumed; this, divided by 10, gives the percentage of acid in the sample tested. This method admits of great accuracy.

75. Practical test of the strength of Acetic Acid

75.    Practical test of the strength of Acetic Acid. A less accurate, but more convenient method for practical purposes, is as follows:- To 100 or 1000 parts (or grains) of a sample under inspection, add cautiously from a weighed quantity of powdered pure dry bicarbonate of potassa, sufficient to produce exact neutralization; carefully re-weigh the bicarbonate unconsumed. Double the loss in grains will indicate the percentage of acid in the liquid tested.

76. Ure's Test of the strength of Acetic Acid

76.    Ure's Test of the strength of Acetic Acid. Ure's test gives very accurate results, if the ammonia employed is of the proper specific gravity. To 100 grains of a sample, very slightly reddened with neutral (blue) tincture of litmus, add liquor of ammonia of specific gravity .992 from an acidime-ter (see No. 82 (Acidimeter)) until perfect neutralization is effected, indicated by the original blue color of the litmus being restored. The number of acidimetric divisions of ammonia expended, multiplied by 51 (for dry) or by 60 (for glacial) and the product divided by 100, will give, respectively, the percentage of dry or glacial acid in the sample. Thus:- if a sample of vinegar takes 10 acidimetric divisions of ammonia to neutralize it, then 10 multiplied by 51, and divided by 100, gives 5.10, equivalent to 51/10 per cent, of dry acid:- or, 10 multiplied by 60 and divided by 100, gives 6 per cent, of glacial or hydra ted acid in the sample.

77. Lire's Test, by Grains, of the strength of Acetic Acid

77. Lire's Test, by Grains, of the strength of Acetic Acid. The same strength of ammonia is to be used in the acidimeter as in the preceding test, and the number of grain-measures of ammonia employed for a multiplier instead of acidimetric divisions. The only difference is, that the product in each case must be divided by 1000 instead of 100, to give the percentage of acid.