[31] Tables are given in the Appendix for calculation by specific gravity; but direct analysis of the acids is the most certain.
Observe that the numbers in the calculation correspond to the atomic weights recently given; and that the amount of water is derived from the total atomic weight, viz. 192, minus the sum of the weights of both acids.
Hence if the samples of acid employed are too weak for the purpose, the formula for the water gives a negative quantity.
The weight of mixed acids produced by the formula is 192 grains, which would measure somewhere about two fluid drachms. Ten times this quantity forms a convenient bulk of liquid, in which about 50 or 60 grains of Paper may be immersed.
In weighing corrosive liquids, such as Sulphuric and Nitric Acid, a small glass may be counterbalanced in the scale-pan, and the acid poured in carefully. If too much is added, the excess can be removed by a glass rod, or by "the pipette" commonly employed for such a purpose.
The following example of a calculation similar to the above may be given:—
| 100 | parts of the | Oil of Vitriol | = | 76·65 | real acid. | ||||||||||||||||||
| " | " | Nitric Acid | = | 65·4 | real acid. | ||||||||||||||||||
| |||||||||||||||||||||||
Multiplying these weights ten times, we have
| Oil of Vitriol | 1043 | grains. | |
| Nitric Acid | 825 | " | |
| Water | 52 | " | |
| —— | |||
| Total weight of the Nitro-Sulphuric Acid | } | 1920 | grains. |