Immediate Delivery. Write for our booklet on Blood Chemistry C. M. SORENSEN CO., Inc., Dept. K GENERAL DISTRIBUTORS 177 East 87th Street NEW YORK Students' Chemistry Desk No. 862. Exposed plumbing and troughs. Accommodates sixteen students working in sections of eight "Without Qualification” To praise a manufactured product "without qualification" implies that it occupies a unique and unusual position in its field. We have always claimed for Kewaunee this position in the field of School Laboratory Furniture, and it is refreshing to have our opinion endorsed so completely. A well known California Principal wrote as follows: "Without qualification I would pronounce your products the finest human genious and skill has yet produced. I heartily appreciate your effort to coordinate your labors with ours in the school room, in an endeavor to raise the standards of cleanliness, economy of time, and efficiency among our young people. It would be difficult for me to suggest a real improvement upon your laboratory furniture." Address all inquires to the factory at Kewaunee. Electric Vacuum Furnaces for obtaining very high temperatures The Arsem Vacuum Furnace is a product of the Research Laboratory of the General Electric Company. It produces temperatures sufficient to melt platinum, iridium and similar metals and such materials as slags, refractories, etc. The following are some of its various uses: Preparation of metals, alloys and various compounds. Determination of melting points by an optical pyrometer or by reference to Calibration of optical pyrometers. Distillation of refractory substances for separation or purification. Study of equilibrium in the reaction depending upon the pressure of the This furnace comprises an electric heater enclosed in a vacuum chamber. Two types are made-a vertical type, large and small, and a box type for still greater capacities. For producing the vacuum required in the Arsem furnace, a two-stage rotary oil-sealed pump, also developed by the G-E Research Laboratory, is recommended. Our general office at Schenectady will be glad to supply further information. General Electric General Office Company ARTHUR H. THOMAS COMPANY WHOLESALE, RETAIL AND EXPORT MERCHANTS LABORATORY APPARATUS AND REAGENTS WEST WASHINGTON SQUARE PHILADELPHIA, U. S. A. SCIENCE FRIDAY, NOVEMBER 12, 1920 CONTENTS THE PROTEINS AND COLLOID CHEMISTRY1 I THE proteins, like certain other constituents of protoplasm, are colloidal in character, i. ., they are not able to diffuse through animal membranes which are permeable to crystalloids. For this reason a number of authors have tried to explain the behavior of proteins from the viewpoint of the newer concepts of colloid chemistry. Foremost among these concepts is the idea that the reactions be tween colloids and other bodies are not determined by the purely chemical forces of primary or secondary valency but follow the rules of "adsorption." Although a number of authors, during the last twenty years, e. g., Bugarszky and Liebermann, Hardy, Pauli, Robertson, Sörensen, and others, have advocated a chemical conception of the reactions of proteins, their experiments failed to convince the other side since these experiments could just as well be explained on the basis of the adsorption theory. There were two reasons for this failure. First, the experiments did not show that ions combined with proteins in the typical ratio in which the same ions combine with crystalloids. This proof only became possible when it was recognized that the hydrogen ion concentration of the protein solution determines the amount of ion entering into combination with a protein, and that therefore the ratios in which different ions combine with proteins must be compared for the same hydrogen ion concentrations. Since the former workers were in the habit of comparing the effects of 1 Address delivered before the Harvey Society, October 16, 1920. The writer's experiments, on which this address is based, have appeared in the J. Gen. Physiol., 1918-19, I., 39, 237, 363, 498, 559; 1919-20, II., 87; 1920-21, III., 85. |