As the cubic centimètre bears the same relation to the gramme that the grain-measure bears to the grain, the one system may be substituted for the other, with no difference in the results excepting that, by the metrical system, all the quantities will be expressed in relation to a weight (the gramme) which is more than fifteen times as great as the British grain.
In practice it will be found convenient in substituting metrical for British weights and measures, to reduce the values of all numbers to one-tenth by moving the decimal points, and this has been done in the tables appended to the descriptions of the volumetric solutions. The quantities indicated in the Pharmacopœia, which in grains and grain-measures can be conveniently used, would be found inconveniently large if the same numbers of grammes and cubic centimètres were employed.
The following apparatus is required in the preparation and use of these solutions.
For British weights and measures:
1. A flask, which, when filled to a mark on the neck, contains exactly 10,000 grains of distilled water at 60°. The capacity of the flask is therefore 10,000 grain-measures.
2. A graduated cylindrical jar which, when filled to O, holds 10,000 grains of distilled water, and is divided into 100 equal parts.
3. A burette. A graduated glass tube which, when filled to O, holds 1000 grains of distilled water, and is divided into 100 equal parts. Each part therefore corresponds to 10 grain-measures.
For metrical weights and measures:
1. A glass flask which, when filled to a mark on the neck, contains 1 litre, or 1000 cubic centimètres.
2. A graduated cylindrical jar which, when filled to O, contains 1 litre (1000 cubic centimètres), and is divided into 100 equal parts.