In practice it will be found convenient, in substituting metric for British weights and measures, to reduce the values of all the 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; for the quantities indicated in the Pharmacopœia, which in grams and gram-measures can be conveniently used, would be found inconveniently large if the same numbers of grammes and cubic centimetres 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° F. (15°-5 C.) The capacity of the flask is therefore 10,000 grain-measures.
2. A graduated cylindrical jar which, when filled to 0, holds 10,000 grams of distilled water, and is divided into 100 equal parts.
3. A burette. A graduated glass tube which, when filled to 0, holds 1,000 grains of distilled water, and is divided into 100 equal parts. Each part therefore corresponds to 10 grain-measures.
For metric weights and measures:—
1. A glass flask which, when filled to a mark on the neck, contains one litre or 1,000 cubic centimetres.
2. A graduated cylindrical jar which, when filled to 0, contains one litre (1,000 cubic centimetres), and is divided into 100 equal parts.
3. A burette. A graduated tube which, when filled to 0, holds 100 cubic centimetres, and is divided into 100 equal parts. (One cubic centimetre is the volume of one gramme of distilled water at 4° C.[1] (39°-2 F.) 1,000 cubic centimetres equal one litre.)
- ↑ It is customary to make the measurements with metric apparatus at 60° F. (15°-5 C.)
