A JVUW PROCESS FOR PRESERVATION OF WOOD. 229 



gradually deposited, as the timber matures, lignine, a hard concretion 

 which makes up the greater part of the volume in hard woods, such as 

 ebony, guaiacum, oak ; in knots, the shells of nuts, etc. Wood, further, 

 contains sap, which holds in suspension gummy materials, nitrogenous 

 and albuminous substances, coloring-matters, etc. ; these are the ele- 

 ments of decay in wood. Inasmuch as they offer to animal and plant- 

 parasites an abundance of agreeable food, they undergo decomposition 

 more or less rapidly, determining, by their own decay, the decay of 

 all the other elements of the wood. 



If we succeed in expelling these essentially putrescible materials, 

 or fixifig them in unalterable combinations, we thus prevent their de- 

 composition, and, in consequence, that of the other more resistant 

 orojanic substances, cellulose and ligjnine. A certain number of ob- 

 served facts seem to demonstrate that the action of tannin upon vege- 

 table tissues must be analogous to that which is exercised upon animal 

 tissues — operating in the vegetable tissues a kind of tanning, which 

 will have for result the formation of hard and imputrescible albumin- 

 ous tannates, quite analogous to the gelatinous tannate products in 

 the tanning of skins. 



Thus, the sizing of wines is effected as well with the white of an 

 ^gg (albuminous matter) as by isinglass (gelatinous matter). The 

 tannic acid contained in the wine forms with either of these mate- 

 rials a solid net-work, which envelops and precipitates the lees to the 

 bottom of the cask. An infusion of oak-bark preserves the skins of 

 animals, and is also employed to protect from rotting the nets of hunt- 

 ers and fishermen. In fine, among exotic or indigenous woods, soft or 

 hard, the most resistant are the richest in tannic acid, as among indige- 

 nous woods the oak and the chestnut; the first remarkably hard, the 

 second soft enough, are both preserved during many years, and we can- 

 not doubt that this is owing to the influence of the tannic acid with 

 which they are impregnated, which, after the cutting of the wood, 

 reacts upon the azotic and albuminous materials contained in their 

 capillary vessels. We may therefore conclude that the injection of a 

 solution of tannic acid into the various species of woods will assure 

 their preservation, by putting them, in a chemical point of view, in 

 conditions analogous to those in which we find the oak after it has 

 been felled. 



But it is not enough to protect soft wood from rotting; it must 

 also be hardened ; and though by the action of tannic acid we in some 

 measure attain this end, the soft materials in the sap-vessels being 

 transformed, still it is important that we should give to woods that 

 are naturally soft a higher degree of hardness, in order to fit them for 

 industrial uses. 



I accomplish this object by the intervention of the remarkable 

 property of tannate of iron, which, perfectly soluble^ and even color- 

 less, in a state of protoxide, is, under the influence of air, transformed 



