. Contributions. Biology. [Reprinted from Science, N. 6'., Vol. XXVIIL, No. 7^5, Page 7So, November SO, loos'] A VACUUM STOPCOCK During the winter of 1908 work was under- taken on the gas production of Bacillus coli in synthetic culture media. The method of work consisted of growing the organism in high vacuum. In the course of this work considerable difficulty was experienced in maintaining absolutely tight stopcocks and as a result a stopcock was devised that appears to satisfy the conditions for a gas-tight stop- cock. The ordinary stopcocks had to be reground with jeweler's rouge, and whil
. Contributions. Biology. [Reprinted from Science, N. 6'., Vol. XXVIIL, No. 7^5, Page 7So, November SO, loos'] A VACUUM STOPCOCK During the winter of 1908 work was under- taken on the gas production of Bacillus coli in synthetic culture media. The method of work consisted of growing the organism in high vacuum. In the course of this work considerable difficulty was experienced in maintaining absolutely tight stopcocks and as a result a stopcock was devised that appears to satisfy the conditions for a gas-tight stop- cock. The ordinary stopcocks had to be reground with jeweler's rouge, and while this precaution rendered the stopcock gas-tight under con- stant temperature conditions, it was found that the changes in temperature from room. Fig. 1 to incubator caused the two ground surfaces, assisted by the resilience of the lubricant, to separate and thus make the stopcock leak. To overcome these difficulties the stopcock had to be tied into place and mercury placed in the exposed lead. The stopcock devised to overcome these dif- ficulties is explained by the two diagrams. The passage from X to Y leads through an obliquely drilled plug as in the ordinary im- proved vacuum stopcock. At 4 a small bulb takes the place of the ordinary open end. Into the center of the plug, and in the same plane as the oblique drilling, a drilling is made as far as the level of the lead X. From this point it continues at a right angle as indicated in the diagram. The operation of the stopcock is as follows. The stopcock be- ing in the position indicated in Fig. 1, the plug is turned throiigh 180°, thus bringing it into the position indicated in Fig. 2. The stopcock is then connected with the pump and the small bulb exhausted. Turning the plug through another 180° will open the passage from X to F and then it may be opened and closed at will without the small bulb A ever coming into communication with the passage. In the above arrangement the atmosphere is exerting its pressure to hold the
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