names tan, tannin^ and tanning principle given it by the French 

 chemists. To M. Proust, however, we are indebted for the inves- 

 tigation of the nature and properties of tan, and of the methods by 

 which it is obtained in a separate state. Much curious and im- 

 portant information has been obtained by the experiments of Sir 

 Humphry Davy, on the constituent parts of astringent principles, 

 and on their operation in the business of tanning, and to the papers 

 of that gentleman, which we understand are founded on practice, 

 we shall be chiefly indebted for the rules hereafter given, as guides 

 to the English tanner. 



Tan exists in a great number of vegetable substances, but 

 it may be procured most readily, and in the greatest purity from 

 nut-galls and catechu. Nut-galls, are, as most of our readers 

 know, excrescences formed on the leaves of the oak by the puncture 

 of an insect which deposits its eggs upon them. The best are 

 known by the name of Aleppo-galls, imported in large quantities 

 into this country for the use of dyers, calico-printers, &c. They 

 are hard like wood, round, often nodulated on the surface, of an 

 olive-green colour, and of an excessively disagreeable taste. They 

 are, in a measure, soluble in water, and what remains is tasteless, 

 and possesses the properties of the fibre of wood. A very great 

 proportion of water is necessary to carry off everything soluble. 

 It has been ascertained that one hundred and fifty English pints 

 of water are necessary to carry off" whatever is soluble in a pound 

 troy-weight of galls. The soluble part of nut-galls consists chiefly 

 of five ingredients, viz, tan; extract; gallic-acid; mucilage; and 

 lime: but tan constitutes more than two-thirds of the whole. 

 Hence the importance of nut-galls and oak-bark in the art of 

 tanning, of which the following is a brief description. 



Hides quickly become putrid when in a moist or wet state, but 

 may be preserved for a great length of time by being perfectly 

 dried, but then are hard like horn, and not fit for any useful pur- 

 pose. These inconveniences are obviated by tanning, and they 

 then take the name of leather. To tan a hide, is to saturate it 

 with tannin, or the astringent principle of vegetables, and by 

 that means, to render it incorruptible. We shall not here dwell 

 upon the theories by which the operations and the effect of tanning 

 have been explained; but shall content ourselves with observing 

 that M. Seguin has shown that the tannin unites itself with the 

 gelatine which forms almost the whole of the hide, and that there 

 thence results a new substance possessing properties altogether 

 distinct. In order to prepare a hide for receiving the tan, it is 

 necessary to begin by removing the hair, separating the adhering 



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