The nature of the reaction between tannin or mineral salts and skin substance is still unknown. Many interesting theories as to the reaction have been ad+anced and much experimental work has been performed in an effort to support or disprove them; the whole question is still, however, quite unsettled. It is improbable that any really fundamental progress in this particular problem will he made until a clearer knowledge of the chemistry and physics of the skin proteins is gained. We believe, however, that a t that time mineral tanning (chrome, a t least) will be found to be a purely chemical reaction and that in vegetable tanning we deal first with an adsorption of the tannin bodies by the skin, followed by a slow chemical reaction. Many interesting scientific problems in the ancient industry of tanning remain unsolved, problems which are attracting many younger men of science. These problems are interesting not alone in themselves but because of the important bearing their solution will have in pure science, in various technical fields and in many phases of medical science. We will instance only a few of the questions which must still he answered. (1) What is the actual mechanism of the swelling which occurs when skin (or any other protein tissue) is subjected to the action of acids or alkalies? (2) What is the structural arrangement of the protein molecules of skin? (3) In what manner do electrolytes and non-electrolytes combine with skin? (4) What is the structural arrangement of the molecule in the various solutions of chrome salts used in tanning? ( 5 ) What is the composition of the vegetable tannins and to what extent does their degree of dispersion in aqueous suspension influence their action on skin? How may their dispersity he controlled? Aside from its purely scientific interest, tanning is of importance to the general public which wears and uses leather. Good shoes are an important item in the world's economy and human health. And to the industrialist, whatever his specific interest may be, there is a useful lesson to be learned in the fact that so old an industry as leather manufacture has found that the substitution of science for empiricism has a sound economic basis and is, indeed, its only safe means of preservation.
Museum Shows Motion of Smoke Molecules. New Yorkers can now see the motion of the molecules in smoke which they breathe or exhale. A new exhibit at the Museum of the Peaceful Arts in New York makes this visible. The visitor blows a puff of cigarette smoke into a funnel, where it passes under a high power microscope. Under the microscope, tiny smoke particles can be seen vibrating back and forth. This motion is caused by the bombardment of the partides by the constantly moving molecules of air around them, and is lmown to scientists as the Brownian movement.Scintce Serdcc
