It may be of interest to give the figures used in the preceding lines in tabular form.
| Limed skin | Puered skin | |||
| Density of wet skin | 1 | ·063 | 1 | ·053 |
| Per cent. of water found | 80 | ·63 | 78 | ·2 |
| " " calculated | 79 | ·50 | 79 | ·9 |
| " of ash on wet skin | 1 | ·71 | 1 | ·17 |
| " of fat " " | 0 | ·151 | 2 | ·6 |
| Density of dry ash-free skin substance | 1 | ·3970 | 1 | ·3356 |
In addition to the diminution of the density of the skin by puering, the increase of fat is very marked.
The percentage of water referred to the wet skin may be calculated from the formula
v2 – v1/1 – v1 × 100
where v1 = specific volume of the dry skin.
v2 = specific volume of the wet skin.
The specific volume of the dry skin (v1) may be calculated from the specific volume of the wet skin (v2), the percentage of water (w) being known by the following formula:—
| v1 = | v2 – w/100 | , |
| 1 – w/100 |
and by comparing the volume thus obtained with the volume determined by direct experiment, the amount of contraction is ascertained. In the case we have been considering (viz. limed skin with 80 per cent. water)
| v2 calculated | = 0·955 |
| v2 found | = 0·941 |