The volume of gas is now read and after absorption in the bulb K and drawing back into B, the process of leveling and reading is repeated in the same manner. These readings give the volume of the gas absorbed a t the same molecular concentration as the gas in A when the apparatus was set up. The reading, therefore, need only be multiplied b y the factor found t o apply under those conditions. I n the bottom of the bath C there is a Bunsen valve which, by turning on the filter pump a t the top, allows a current of air t o pass through the bath C thus keeping the liquid well stirred. The tube D should be of small bore and of sufficient length t o allow for the variations of temperature from season t o season. The above modification may be fitted t o the ordinary Parr apparatus or gas pipette by inserting the stopcock E. The writer .wishes to thank Professor George H. Failyer for a suggestion that led t o the above modification. CHEMICALLABORATORYKANSASEXPERIMENT STATION KANSAS STATEAGRICULTURALCOLLEGE MANHATTAN
IMPROVED APPARATUS FOR TESTING THE JELLYSTRENGTH OF GLUES By l3. C. HULBERT
bulb, to force the liquid in the bulb-tube down t o the lower graduation 12, the cock turned to a n intermediate position and the gage read. The principal advantages of this apparatus over others are: The figure obtained is not influenced by the condition of the surface of the sample, such as formation of a tough “skin,” rapid change of temperature during the test, etc. The error due t o supporting a column of water resting directly upon the glue surface, as in another somewhat similar apparatus, is avoided; this is of especial importance in case of glues of low grade. The reading is quickly made and may be repeated three or four times on the same sample, if desired. N o error is introduced either by the apparatus itself or its manipulation ; duplicate samples, tested under like conditions of temperature, etc., give identical readings. The apparatus is simple and inexpensive and may be constructed by anyone having moderate skill in glass working. Glues may be tested either under constant cond,itions of temperature and strength of solution, or compared with a standard glue. The gage scale may be graduated in any convenient way, as by comparison with another type of glue testing apparatus, or with standard glues.
Received November 1 , 1912
SULZBBRGER & SONS Co.
The apparatus consists of a thistle tube, the stem of which is twice bent and contains three bulbs. The two larger are about z cm. diameter and serve a s safety traps ; the smaller is accurately graduated t o contain I cc. Over the mouth of the thistle tube is stretched a diaphragm of thinrubber. The far end of this tube connects through a 4-way stopcock with a gage consisting of a mercury filled U tube having its far arm extended upward and of smaller bore, this arm containing water or other liquid above the mercury. A rubber bulb is attached to one arm of the stopcock, the remaining arm being left open to the air. The sample of gluejelly is raised by means of the adjustable stand until the liquid in the bulb tube reaches the upper graduation wz,and the stand secured in this position, the stopcock meanwhile being set to connect arms A,B,C (see diagram). The cock is now turned to connect arms A , B , D and enough air forced into the system by means of the rubber
KANSAS CITY, Mo.
A USEFUL VALVE B y NATHAN S M I T H Received November 15, 1912
This simple “homemade” valve has proved very efficient in preventing the “suckback” which usually results in vacuating desiccators by water s u c t i o n , when the pressure is suddenly lowered. The valve may also be a d v a n t a g e o u s l y employed in the Kjeldahl nitrogen determination. A small evenly drawn tube, A (the tip of an old pipette serves the p u r p o s e ) , is fitted with a piece of r u b b e r , B, u-hich a c t s as a valve. A piece of w i r e , C, i s d r a w n through t h e center of t h e valve and bent a s shown. Another piece of glass tubing, D, is fitted over t h e valve t u b e l j y means of rubber connection, E. LABORATORY SCHIEFFELIS & Co., N E W Y O R K CITY
t To
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rom Des iccator
