The figures are all percentages calculated on the dry weight of the skin.
Munro Payne (Tanners’ Year Book, 1905, p. 75) gives the following amounts of lime as Ca(OH)2 in limed hides, calculated on dry weight at 212° F.:—
| Direct from limes | max. | 3·859 per cent. | |
| " " | min. | 2·836 | " |
| Limed for buff | 4·621 | " | |
| Limed for tanning | 3·7659 | " | |
| Ditto after bating | 0·689 | " | |
| Calf limed | 2·601 | " | |
| Calf bated | 0·1215 | " | |
| Goat limed | 5·613 | " | |
| Goat bated | 1·268 | " | |
[7] From the molecular weights it will be seen that 74 grm. of calcium hydrate, equivalent to 56 grm. of lime (CaO), require 73 grm. of HCl gas for neutralization. This quantity of gas is contained in 265 grm. of commercial hydrochloric acid of 18° Bé., or about 230 c.c.—that is, for 100 grm. CaO, 410 c.c. of 18° Bé. acid are required; hence for the 100 kilos wet grain containing 400 grm. CaO, 1640 c.c. of acid are required for complete neutralization. It is impracticable to use this amount of acid, for the reasons stated above.
[8] Tanners’ Year Book, 1911, p. 59.
[9] See Chapter III.
[10] See also L’Acide Butyrique dans la Tannerie, Urbain J. Thuau, Le Cuir, Aug. 1910. Also Collegium, 1910, pp. 347, 363.
[11] Le déchaulage des Peaux en tripe, Ettore Guisiana (Turin), Coll. 1910, p. 14.
[12] Verfahren zum Beizen von Haüten, Ledertechnische Rundschau, No. 24, 1910. Coll. 1910, p. 372.
[13] When the puer is dirty it should be diluted with water and strained through a bag, or the diluted puer may be put into a tub and the heavy grit and dirt allowed to fall to the bottom of the vessel. Puer from hunting kennels is usually clean enough to use without this process.