CHEMICAL SCIENCE. 327 



It will probably replace to some extent vellum in book-binding- ; it will 

 furnish material for legal documents, such as policies of insurance, scrip 

 certificates, &c. ; it will take the place of ordinary paper in school-books, 

 and other books exposed to constant wear. Paper, afier having been 

 printed either from the surface or in intaglio, is still capable of conver- 

 sion by Mr. Gaine's method, no part of the printed matter being oblit- 

 erated by the process. Parchment-paper also promises to be of value for 

 photographic purposes, and also for artistic uses in consequence of the 

 manner in which it bears both oil and water-color. 



ACTIOX OF TAXXIX UPOX SKIX. 



The first of a series of investigations has been recently laid before the 

 Academy of Sciences, Paris, by M. Payen, undertaken with a view of ar- 

 riving, if it be possible, at a knowledge of the phenomena which arc going 

 on during the operation of tanning, and to establish a theory of this opera- 

 tion, still so obscure to the chemist. In this first part, he has endeavored 

 only to examine thoroughly and show the generality of a fact, which he had 

 observed several years ago. This fact is, that there exist in the skin two 

 portions which present different properties, when they have undergone the 

 action of tannin. One of these is easily disaggregated, soluble in ammonia- 

 water, the other preserves its fibrous texture, and resists the action of the 

 re-agent, although frequently renewed. The saturation of the skin by the 

 tannin takes place long before the time practically required for good tan- 

 ning ; and requires for the two parts much less tannin than gelatine. The 

 compound formed with the tannin, by the less cohesive parts of the skin, 

 when it has been dissolved in ammonia, is changed in dissolving; it under- 

 goes, besides, a considerable loss of nitrogen during its evaporation to dry- 

 ness. The effects of long-continued tanning cause the gradual solution of 

 the less cohesive portions united with the tannin, and consequently a rela- 

 tive increase of the quantity of resisting fibrous material. The product, in 

 this case, must therefore be both more pliable and more tenacious. The 

 friable soluble portion which remains in the tanned leather is unstable ; in 

 dissolving, it may withdraw considerable quantities of the azotized sub- 

 stance ; and it is thus, perhaps, that the less cohesive part of the skin is 

 removed during the long operations of tanning. These arc, in substance,' 

 the remarks which result from the observations and analyses reported in 

 detail by M. Paycn. The author proposes to examine successively all the 

 operations of tanning, and to study separately the effects produced by lime, 

 soda, by ammonia, the formation of which is determined by the foregoing 

 bases, by dilute sulphuric and lactic acids, &c. L'Institut. 26th November. 



OX THE mEPARATIOX OF PUKE GRAPE-SUGAR, 



Commercial honey, as crystalline as possible, is spread upon porous tiles. 

 The white crystalline residue is dissolved in alcohol, and purified by re-crys- 

 tallization; if necessary, also with animal charcoal. The honey yields about 

 one-fourth of its weight of grape-sugar. Jour n. fur Prald. Chem. 



