January 15, 1935
ANALYTICAL EDITION
reaches this in 35 minutes, and stock F in 23 minutes. It is evident that machines which evaluate on vertical compression and time only give results which may be greatly in error. C
e
400 200 ‘C.
f = Good Road Test G 2 Poor Rod Test I
67
SUMMARY A new machine for evaluating breakdown characteristics of rubber compounds, described above, not only measures the flexing forces a t all times, but also indicates the point of initial failure, accurately, before complete destruction of the test specimen takes place. The theoretical value of the machine has been revealed by the indication of an unexpected structural change which takes place in the rubber during flexing. This change manifests itself in a marked stiffening of the stock which increases until initial failure occurs. The practical value of the machine has been demonstrated by its ability to simulate different types of service conditions, as shown by the excellent correlation of the authors’ tests with the manufacturers’ road tests on commercial compounds.
LITERATURE CITED FIGURE29. STEPPEDINCREASE HORIZONTAL LOAD TEST Commercial solid tire stocks
WTo duplicate service conditions as nearly as possible, it was felt that the stocks should be tested under the same loading conditions. The deflections would then be dependent on the modulus and stiffness of the compounds. The stepped increase horizontal load test was used and temperatures were taken a t the center of the specimen and plotted against time (Figure 29). Both specimens were subjected to the same system of loading, which was 3.2 kg. (7 lb.) at the start increased by 4.1 kg. (9 lb.) a t six 5-minute intervals. Stock G failed in 30 minutes, while stock F did not fail even after 90 minutes of testing. At the end of 90 minutes the temperature was dropping, indicating that failure due to heat was impossible. The stocks were then compared under the matched horizontal load conditions of testing. Both stocks were first run in the regular way, as shown on Figure 27, with a vertical load of 261 kg. (575 lb.) and a horizontal deflection of 0.533 cm. (0.210 inch). Stock G was again tested and the horizontal load adjusted by means of the handwheel to match the greater load of stock F. Stock G failed in considerably less
Tim in Hinubs
FIGURE 30. MATCHED HORIZONTAL LOADTEST Commercial solid tire stocks
time than stock F, which again checks the manufacturers’ road tests. Stock E’ was again tested and the horizontal load adjusted to match the lesser load required by stock G. Stock F withstood the less severe conditions and the specimen started to decrease in temperature after 60 minutes, indicating that no failure due to heat would occur. This test is recorded on Figure 30.
(1) Abbott, IND. E m . CHEM.,20, 853-7 (1928). (2) Cooper, Ibid., Anal. Ed., 5,350-1 (1933).
(3) Perrott, G. St. J., and Kinney, S. P., J. Am. Ceramic Soc., 6.
417-25 (1923). (4) Schopper, Louis, Catalog 415, p. 25, Leipzig, Germany; American
agent, Testing Machines, Ino., New York, N. Y . RECEIVED September 15, 1934. Presented before the Division of Rubber Chemistry a t the 88th Meeting of the American Chemical Society, Cleveland, Ohio, September 10 to 14, 1934.
Wash Bottle for Quantitative Work EDWINJ. DEBEER 1254 North 28th St., Philadelphia, Pa.
I
T FREQUENTLY happens in analytical work that a precipitate must be washed or transferred from one container to another with a limited quantity of reagent. By means of the device illustrated, a measured amount of liquid. may be directed in such a way as to aid in stirring up and dislodging the precipitate. The tube A is sealed into the bottom of the inner reservoir and the end cut off a t r i g h t angles. A small rounded section of glass rod is dro ped into the inverted tube anzthe end carefully and evenly heated with a small hot flame until the contracting glass has almost sealed the opening. This simple valve will permit pressure to be built up within the inner reservoir, so that its contents may be blown out. It will also prevent the flow of liquid from the outer t o the inner reservoir following sudden changes in pressure. A small vent, indicated at E, may be cut into the stopper in case too much air escapes through the valve. The d i a m e t e r of the inner reservoir and the dedh t o which the delivery t u b e ; B, extends, govern the volume of liquid expelled a t a n y one time. The inner reservoir is filled by pinching the rubber connection, C, thus shutting off the delivery tube, and applying suction at the mouthpiece. Excess liquid will drain back into the inner reservoir. It is emptied in the usual manner, care being taken not t o incline the wash bottle too much. R ~ C ~ I VOctober ED 31, 1934.
