146 SHEET FABRICS. [V. 



force, hasten the combination of tannin. The same ends ap- 

 pear to be also attained by the free use of lime, whereby the 

 hide is swelled and its pores opened. The precise action of 

 acid is not well ascertained, except that the process is short- 

 ened. These are the main principles by which a shortened 

 process of tanning has been accomplished. Where lime has 

 been freely used, acid liquors generally follow, and the hide is 

 so puffed and porous, that tanning becomes expeditious ; but 

 the hide has been torn and rent asunder, and the organized 

 structure must be necessarily impaired, and the strength and 

 firmness of the leather consequently diminished. It will be 

 observed that in the older processes the change was so slow 

 that the organized structure of the skin was not impaired ; that 

 but little matter was removed from the hide, while a quantity 

 was added to it. In accelerating the change, a portion of the 

 matter is removed by solution while undergoing transformation, 

 before it can unite with, and become fixed by, the tannin. 

 Hence the greater looseness and levity of leather prepared by 

 the more modern and rapid processes. It may perhaps be 

 stated as an ascertained fact, that leaving the side in the vats 

 during two years instead of one, the increase of weight and 

 quality thereby, compensates for the loss of time, by paying 

 a fair interest on the capital invested. — J. 0. B. 



A patentee, in Lond. Journ. xxxvi. 310, proposes a combi- 

 nation of the white leather (alum and salt) process, with the 

 tanning process by means of catechu. Another (Lond. Journ. 

 xxxvi. 319) suggests the use of sulphuret of calcium instead 

 of lime for unhairing. 



Since liming tends to lengthen tanning, by preventing the 

 more rapid union of tannin with gelatin, Turnbull treats the 

 hides after liming with a concentrated solution of sugar, so 

 that the access of air is prevented during the action of the 

 bark-liquors on the hides, and the formation of gallic acid 

 thereby prevented. In this manner, the same amount of 

 leather is obtained in 14 days from lOOSb oak-bark, as has 

 been heretofore obtained in 18 months from 80056 bark. 



Tannin. — Kampfraeyer states, as a result of his compa- 



