Instead of the above calculation, we may multiply the weights of the respective acids required to expel 1 gr. of carbonic acid (as exhibited in the following table) by the number of gr. of dry carbonic acid evolved during the above operation. The product represents the per-centage strength, when 100 gr. of the acid have been examined. When only 50, 25, 20, or 10 gr. have been tested, this product must, of course, be doubled, quadrupled, &c., as the case may be.
Table II.
| Multipliers. | |
| Acetic acid (anhydrous) | 1·159 |
| Acetic acid (hydrated or glacial) | 1·364 |
| Citric acid (crystallised) | 1·523 |
| Hydrochloric acid (dry or gaseous) | ·829 |
| Hydrochloric acid (sp. gr. 1·16) | 2·478 |
| Nitric acid (anhydrous) | 1·227 |
| Nitric acid (sp. gr. 1·5) | 1·523 |
| Nitric acid (sp. gr. 1·42) | 2·045 |
| Oxalic acid (crystallised) | 1·432 |
| Sulphuric acid (anhydrous) | ·909 |
| Sulphuric acid (sp. gr. 1·8485) | 1·114 |
| Tartaric acid (anhydrous) | 1·500 |
| Tartaric acid (crystallised) | 1·705 |
Even this easy calculation may be avoided, in technical analysis, by simply taking for the assay such a weight of the respective acids as is capable of disengaging exactly 10 gr. of dry carbonic acid from the bicarbonate. In this case, the loss of weight in grains, from the operation, multiplied by 10, at once indicates the exact per-centage strength sought. The proper weight of any acid to be taken to give per-centage results is found by simply dividing ten times the equiv. of that acid by 44. For, taking sulphuric acid as an example,
as— 44: 49 :: 10 : 11·1318
or 11·13 nearly.
On this principle are obtained the weights to be taken, as given in—
Table III.
| Grains. | |
| Acetic acid (anhydrous) | 11·59 |
| Acetic acid (hydrated or glacial) | 13·64 |
| Citric acid (crystallised) | 15·23 |
| Hydrochloric acid (dry or gaseous) | 8·29 |
| Hydrochloric acid (sp. gr. 1·16) | 24·78 |
| Nitric acid (anhydrous) | 12·27 |
| Nitric acid (sp. gr. 1·5) | 15·23 |
| Nitric acid (sp. gr. 1·42) | 20·45 |
| Oxalic acid (crystallised) | 14·32 |
| Sulphuric acid (anhydrous) | 9·09 |
| Sulphuric acid (sp. gr. 1·845) | 11·14 |
| Tartaric acid (anhydrous) | 15·00 |
| Tartaric acid (crystallised) | 17·05 |
2. A convenient modification of the preceding method of acidimetry consists in using the common apparatus figured in the margin and employing fused chloride of calcium to dry the evolved carbonic acid gas, instead of concentrated sulphuric acid. The mode of conducting the process and obtaining the results is precisely the same as in that last explained, and need not, therefore, be repeated. In this case, however, suction must be applied to