152 ABSTRACTS OF CHEMICAL PAPERS APPARATUS, ETC. Collodion Membranes for Ultrafiltration and Pressure Dialysis. G. S. Walpole. (Biochem. J., 1915, 9, 284-297.)-CylindricaI oollodion bags, prepared by coating the inside of a test-tube with collodion solution, allowing the solvent to evaporate partially, then adding water and removing the film, have been used for simple ultrafiltration and dialysis experiments ; but they lack uniformity, are difficultAPPARATUS, ETC.153 of accurate reproduction, and do not withstand any excessive pressure. Much more satisfactory membranes may be made by pouring alcohol-ether collodion solution on to levelled plate glass and then plunging the film, from which the alcohol and ether have more or less evaporated, into water. By keepi:ig as far as possible to constant conditions, these membranes may be described, for purposes of reproduction and as a guide to their properties, by stating the kind of nitrocotton used, the weight of it they contain per sq.em., and the ‘(wetness,” i.e., the ratio of the weight of a piece to its weight when dry. Films containing 8 mgrms. of nitrocotton per sq. em., and weighing, with contained water, 40 mgrms.per sq. cm., have been found to retain all antigens. I t is suggested that the channels through the gel structure are of uniform size, and that they are sniall and numerous. They may be used i n a filter-press. m7. P. s. New Dip Electrode. G. J. Van Zoeren. ( J . Ailrzer. Ch,em. SOC., 1916, 38, 652-653.)-For determining the electrical conduct,ivity of viscous solutions very rigid electrodes are required, so that the distance between them may not be altered by the somewhat vigorous stirring which is usually necessary. The electrode illustrated is sufficiently rigid for determining the conductivity of diluted mapie syrup, and also serves well for the determination of the “volumetric lead number ” of such syrups, for which purpose horizontal electrodes are unsuitable, inasmuch as the precipitate settles on them.The electrode is placed in a hard glass cylinder 6.5 CMS. high by 3.7 ems. in diameter, open a t both ends. One end is fitted with a vulcanite cap, B , fastened to the cylinder by means of set screws. i? thermometer and two glass tubes pass through the cap. The tube C allows the air to escape when the electrode is immersed in the E! -€ solution.The platinum connecting wires, which are welded to the electrodes, are protected by being sealed in the tubes, E, in which mercury is placed to connect the electrodes with the hridm lea,dn The eleat8rniien. A . 2,re of N o 30 R. and 6 - - - - - - _. - - - - - -. - - - - - - - - - - - -- - I , -- , -- - - - - - . - . - - - . I -- - S.gauge platinum foil, 2 x 2 cm. squares, set 1 cm. apart. They are firmly fastened together by means of four glass pins as shown, D. The pins have small enlargements 2 inms. from each end, which serve as collars, and prevent the elec- trodes from being crowded together. The ends of the pins pass through the electrodes and are clinched. I n this way they are firmly held in place.An ordinary 100 C.C. beaker may be used to complete the cell. G. C. J. Possible Source of Error in Colorimetric Observations. J. H. Long, (J, Amer. Chem. SOC., 1916, 38, 716-718.)-The prisms of the Dubosc colorimete’r seem to be fastened in their brass sockets by means of a wax which is too soft for the purpose, and which softens enough in summer in Illinois (33” C.) to allow the prisms to drop down a little.Considerable errors may arise if this happens and is.154 ABSTRACTS OF CHEMICAL PAPERS not detected. Such instruments should, therefore, be kept away from heat radiators and sunny positions, and the zero should be controlled whenever the instrument ig used. G. C. J. Grain, Seeds, and other Material. E. G. Boerner. No. 287, 1915; through J.of Agric. Intell. and Plant Diseases, 1915,6, 1688.)-The material is placed in the hopper A, communicating through the valve B and the shield C with the cone D, which is provided at its base with a series of separated ducts, F, having uniform spaces, E, between them. Adjusted to the bottom of the ducts at H is a funnel I, having a spout R Device for Sampling (U.S. Dept. of g g r i c .Bull., at its bottom part. When the valve B is opened the material spreads on the cone D ; then, entering the ducts, passes through them and the inner funnel, and issues through the spout at the bottom into the receptacle T, while all the material which enters the spaces between the ducts falls into the outer funnel and thence into the other container U. As the widths of the ducts are equal to the spaces between the ducts, two equal portions of the A very small 11 sample of the original material can be obtained 1 by adjusting the proportion between the widths of the ducks and the spaces between them; or the material in either T or U may be again put through the apparatus as often as may be required. a original material are obtained. H. F. E. H.