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INDUSTRIAL AND ENGINEERING CHEMISTRY
The next experiments were with dried canned spinach and albino rats. Two-tenths gram daily produced decline, and once decline had begun, raising the amount to 0.8 gram daily failed to check it. If the amount was raised to 0.8 gram daily early enough in the experiment it was possible to secure subnormal growth. Based on experiments with the rat, then, the Osborne and Mendel experiments on dried raw spinach seemed confirmed by dried canned spinach. To settle this point more definitely a further series of tests (Chart IV) was planned. Three series of four rats each, representing two litters, were started simultaneously. Each group was placed on the Osborne and Mendel basal diet, complete in all factors except vitamin B. Group 1was then offered, in addition to the basal diet, 2 grams of dried raw spinach per rat per day and careful account was taken of the amount actually consumed per day. Groups 2 and 3 were treated similarly, but to one was given dried 70-minute process spinach and to the other dried 120-minute process spinach. (This canned spinach was the 2-minute water blanch lot.) The growth curves and the spinach intakes are plotted on the charts. Starting with an intake of about 0.5 gram daily and steadily increasing that intake to a 2-gram daily amount in the last weeks of a 100-day experiment, the rats on dried raw spinach attained better than normal growth. Dried raw spinach can therefore supply the vitamin B requirement of the albino rat, and the amount needed varies between 0.5 and 2 grams daily, depending on the age of the animals.
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The curves of the two groups on the canned spinach, however, are in marked contrast to those on the raw spinach. At first this would Seem to indicate that the canning process had affected the vitamin B content. If we examine the spinach intake figures, however, we see that these rats persistently refused to eat an adequate supply of this spinach. We also see that when the appetites of Series 3 were stimulated by adding 0.1 gram of dried yeast daily to their diet (one-third of the rat's daily requirement of vitamin B when yeast is the sole source), they not only began to gain but at the same time began to eat the spinach. Furthermore, by contrasting the gains of these four rats after adding the yeast we see that those that gain most are those that eat most of the spinach, though their yeast intake is identical. Conclusion
These experiments do not adequately solve the problem stated at the beginning of the paper. If the rat test is a test for vitamin B content the pigeon test results must still be explained. On the other hand this conclusion is drawn as to the effect of canning on the vitamin B content revealed by rat test-via., that canning does affect the product to the extent of making the rat refuse to eat it in adequate quantity unless his appetite is otherwise stimulated, but that the process has not actually destroyed the vitamin, In other words, the experiments differ because this product is not well suited to the test animal, not because of difference in vitamin B content in fresh and canned spinach.
Hydrogen Electrode Vessels for Use with Tannery Liquors' By J. A. Wilson and E. J. Kern A. 1.GALLUN & SONS Co., MILWAUKEE, WIS.
HE large number of requests for a description of the electrode vessels found most suitable for tannery work indicate the desirability of publishing this information, especially since the vessels in question are useful in all hydrogen electrode measurements. The onlv points of novelty claimed are slight modifications of existing types which have been evolved in actual practice in this tannery during the past ten years. Batteries of the vessels described have been used in daily routine during the past few years for all kinds of tannery liquors and, even in the hands of men with no scientific training, have always given satisfactory results. The outer portion of the hydrogen elecHYDROGEN ELECTRODEVESSELSUSED FOR trode vessel A is a TANNERY LIQUORS straight glass tube with a side arm, the lower part of the tube being perforated with holes to assist in the escape of hydrogen. The purified hydrogen gas is passed in through side arm B. The electrode itself is a piece of 22-gage platinum wire from 1 to 2 cm. long sealed in the end of a glass tube which passes through an ordinary cork fitted to the outer tube. The electrode tube is filled with mercury 1 Presented by J. A. Wilson before the Division of Leather and Gelatin Chemistry at the 68th Meeting of the American Chemical Society, Ithaca, N. Y., September 8 to 13, 1924.
and contact with the potentiometer is made by inserting a wire from it into the open end of the electrode tube, The advantages of this type of hydrogen electrode vessel are apparent. The electrodes are so cheap that they can be made up in large quantities and they can be replaced quickly by fresh ones when they become poisoned, which happens frequently when they are used for some kinds of tannery liquors. The use of a wire electrode of small exposed area is advantageous in bringing the system to equilibrium more rapidly, which is desirable in titrating and in liquors that easily poison theelectrode. Dozensof these electrodes should be kept under water ready for use, and i t is desirable to have a number in distilled water with hydrogen bubbling over them, where they may be needed on short notice for liquors which poison the electrode easily. They are readily cleaned, before replatinizing, by dipping into hot aqua regia for a moment. Vessel C is the calomel cell. At point D the tube is sealed off with a platinum wire making electrical contact between the separated portions. The side arm E is filled with mercury, into which is inserted one of the wires from the potentiometer. The bulb of the cell,is filled with mercury covered wth a layer of mercury-mercurous chloride paste, and the cell is kept filled with a saturated solution of potassium chloride and mercurous chloride, which enters the cell from a large reservoir through the side arm F, the flow being regulated by stopcock G. When the cell is being flushed with the chloride solution, the overilow passes out through the capillary side arm H. The solution whose hydrogen-ion concentration is to be measured is poured into dish I . The deep U in the capillary tube prevents contamination of the calomel cell by the tannery liquor, which usually has a lower specific gravity than the solution in the cell. Stopcock G permits flushing the capillary tube after each determination. One of these cells may be used daily for many months without other cleaning.
