In making use of the volumetric solutions a graduated tube or alkalimeter is employed, which when filled to 0, holds 1,000 grains of distilled water at 60°; it is divided into a hundred parts of equal capacity, so that each division will contain ten grains of distilled water at 60°. The graduation should be carefully made, the object being to note, with as much accuracy as possible, the number of measures of the solution required to produce a certain effect. With regard to the alkaline and acid test-solutions, but little need be said. The solution of soda for estimating the strength of acids is so prepared that a hundred measures of the solution contain thirty-one grains of soda; the equivalent of soda being thirty-one, it is evident that this quantity will neutralize an equivalent in grains of any monobasic acid. The solution of oxalic acid for determining the amount of alkali is of such a strength that a hundred measures of the solution contain sixty-three grains of oxalic acid, and are therefore capable of neutralizing an equivalent in grains (sixty-three being the equivalent of crystallized oxalic acid) of any alkali or alkaline carbonate, thirty-one grains of soda, forty-seven of potash, etc, etc.
The following are the directions given in the Pharmacopoeia for the preparation of the volumetric solution of soda and oxalic acid.