16
ANALYTICAL EDITIOhT
Vol. 1. So. 1
Device for Carbon and Hydrogen Analysis of Volatile, Explosive, and Easily Carbonizable Organic Liquids' Manasseh G. Sevag COLUMBIA UNIVERSITY, N E W YORK,N. Y .
HE writer has had occasion t o analyze organic liquids of diverse nature for carbon and hydrogen. Some of these liquids were very volatile, explosive, and easily carbonizable. The usual method for the analysis of organic liquids, which involves the use of a capillary bulb, is unsatirfactory. The making of the bulb, the process of filling, especially the difficulty in filling the bulb with the desired quantity of substance, make i t tedious and time-consuming. A more serious objection to this method, however, is that iii the analysis of compounds which carbonize within the bulb without volatilization, owing to lack of access of oxygen to the carbonized material within the bulb, the combustion is usually incomplete. Various devicer have been advocated from time to time to overcome these objections. The methods proposed by Clarke,2Shoesmith,3Reid,4and Hempe15are time-consuming, and require additional parts for the already complex combustion train. Besides they are mainly employed in special cases. Under pressure of doing numerous analyses a simple device for rapid and general use was developed by the writer. It proved to be not only time-saving, but compact and capable of giving satisfactory results. It is comparable in simplicity with the porcelain boat usually used for analysis of organic solids. Description of Device
nature, has great absorbent capacity for organic liquids and causes the vaporization of the volatile and explosive liquids t o take place gradually during the combustion. It also seems t o have some catalytic action, thus facilitating the combustion of compounds that carbonize readily. Kieselguhr must first be ignited for 20 minutes, in a platinum crucible, or any other suitable may, and kept over phosphorus pentoxide in a desiccator until ready for use. The tube is filled one-third full with the kieselguhr, being supported in the tube by means of two pads 1 cm. thick made of ignited coarse asbestos fibers. The arrangement should be such as to allow the free passage of oxygen throughout the whole length of the tube, thereby permitting the oxygen t o have free access to the liquid that is being burned. The author is of the opinion that this, together with the catalytic effect mentioned above, is responsible for preventing the occurrence of any trace of carbon monoxide. These tubes can be used repeatedly without recharging.
Filling Tube with Ignited Kieselguhr
Analysis of a n Explosive Liquid
Aft'er several reagents had been tried with the view of finding one that would effect a smooth vaporization and slowing down of the explosive violence of the organic liquids during their combustion, it was found that kieselguhr meets these requirements. During initial trials the liquids were burned by niixing them with this reagent in a porcelain boat. Later a short, narrow tube sealed a t one end mas tried. These initial trials finally led to the use of the above device. Kieselguhr,e by virtue of its porous and pulverulent
Using the capillary bulb method, the writer tried to run a combustion of an organic liquid which happened to bc volatile and so explosive that in exploding it threw the bulb out of the boat, breaking a piece from the boat, and causing the bulb instantly t o fuse to a shattered mass. The same difficulty was experienced several times, but by the use of the new device described above no such trouble was experienced, and the following results were obtained: carbon, 84.43 and 82.73 per cent; hydrogen, 15.27 and 15.26 per cent.
T
Weighing of Liquid
Before the tube is weighed it must be subjected to a blank test. In making an analysis the pad 2 is taken out with a pair of forceps and placed on a clean surface, the stopper replaced, and the tube weighed. Stopper 1 is then removed A Pyrex glass or transparent quartz tube 8.5 em. long, and the liquid is introduced dropwise by means of a capillary 6 t o 7 mm. inside diameter and 10 t o 12 mm. outside diameter, pipet on the surface of the kieselguhr, care being taken not has two ground-glass stoppers fitting tightly into each end. to contaminate the side of the tube. Stopper 1 is then reSuch a tube can be easily made in the laboratory from or- placed and the tube weighed. Knowing the approximate dinary Pyrex glass tubing, using small, firm red rubber stop- specific gravity of the substance, one can introduce the exact pers, instead of ground-glass stoppers, and taking care that quantity of substance required for the combustion. Before the tube is introduced into the combustion tube, the stopper no plcce of rubber stopper is ripped off into the tube. 1 iq removed and the pad 2 returned to its original p o s i t i o n ; then t h e stopper in the other end is removed a n d t h e tube introduced quickly into that s e c t i o n of the combustion t u b e ordinarily occupied by a porcelain boat, a n d the combustion started gradually in the usuaI 1 2 3 4 5 way.
1 Received August 10, 1928. Contribution No. 690, from the Department of Chemistry, Columbia University. 2 Clarke, J . A m . Chem. Soc., 34, 746 (1912). 3 Shoesmith, J . Soc. C h e w . Ind.,42, 57 (1923). * Reid, J . A m . Chem. So?, 34, 1033 (1912). 5 Hempel, 2 . ami. Chem., 17, 109 (1878). 6 After bringing t h e use of this device t o a satisfactory perfection, the writer found t h a t Dennstedt, 2. aflgetw. Cham., 18, 1134 (1905), has used kieselguhr t o analyze petroleum, lubricating, and mineral oils.
Analysis of Esters
It is quite well known that the analyses of certain esters offer difficulty in yielding low results for carbon. Thus Skraup' found difficulty in analyzing esters of mucic acid. He ascribed this to incomplete combustion, but Zanetti and 7
Skraup, Moflntsh., 14, 476 (1893).
January 15, 1929
INDUSTRIAL AhrD ENGINEERIiVG CHEMISTRY
Beckmann* suggested that the low results in this particular case were due not only to incomplete comkiustion but to the formation of pyromucates. which they found difficult tp burn completely. They found that, in spite of all precautions, the analyses for carbon, in the case of the esters of n-amyl. n-hexyl, n-heptyl, n-octyl of furoic acid, came out uniformly low, especially in the case of the higher esters, and also in the case of the esters of furoylacetic acid.Q With the use of this new device, however, the analysis of esters of similar nature, such as of a-tetrahydrofurfuryl alcohol synthesized by Zanetti,lo the author obtained very satisfactory results. The most difficult to burn in this series was found to be the isovalerianate of a-tetrahydrofurfuryl alcohol, for which the following analyses (not yet published by authors) were obtained : ~-
* Zanetti and Beckmann, J . A m 9 1
KEW DEVICE
Carbon Found Calcd.
70
Hydrogen Found Calcd.
70
%
%
17 CAPILLARY METHOD Carbon Hydrogen Found Calcd. Found Calcd.
%
70
%
%
Analysis of a Known Highly Volatile Liquid
As a final test two analyses were made of a highly volatile organic liquid compound, benzene, with the following results: Found
CARBON
HYDROGEN Calcd.
Calcd.
Found
70
70
70
70
91.97 92.06
92,30
7.73 7.88
7.69
These results indicate that volatile liquids like benzene can be weighed in this new device and introduced into the combustion tube without any material loss.
Chem. S O ~ .48, , 1067 (1926).
Ibid., SO, 1438 (1928).
OZanetti, Ibid., 60, 1821 (1928).
A New Physical Test for Vulcanized Rubber’ D. D. Wright HOODRUBBER COMPANY, WATERTOWN, MASS.
This test, by use of a sample of new design, subjects the jaws of the testing maTLCANIZED r u b b e r rubber to a combination of tensile and shearing chine (Figure l). The lower is frequently required stresses. Shear, however, is the predominating stress. jaw moves a t the rate of 10 to withstand, not only Certain aged inner tubes have been found which inches (25.4 cm.) per minute. the simple stresses such as deteriorated more when examined by this test than a I n the usual manner readthose of compression, tensile, comparison of their tensile-stress-strain curves with ings of load and elongation and shear, but also the comthose of fresh tubes would indicate. Tearing action are taken up t o and includbined effects such as torsion, seems to be approximated by this test. The effect of ing those at rupture. From tearing, bending, etc. It has overcure in some cases’ has been recorded at earlier these measurements and the been observed that, as some stages by this test than by the tensile criterion. The cross section of the tongue the vulcanized rubber s a m p l e s test is easy to perform and with usual precautions shear-stress-strain curve may age, their resistance to shearshould have an accuracy of approximately 10 per cent. ing and tearing stresses debe plotted and the relative creases inuch faster than their energy to start rupture estiresistance to tensile stresses, as determined under the stand- mated by determining the area under the curve. Figure 3 shows the comparison of the shear-stress-strain curves with ard procedure of rubber-testing. During a study of natural and artificial aging some inner- the usual tensile-stress-strain curves. The reasons that the tube samples, which tested very poorly after the oxygen bomb shear-stress-strain curves do not exactly coincide with the (50 hours a t 60” C. and 20.4 atm.), were filed for further tensile-stress-strain curves seem to be: (1) Different widths observation. As these tubes aged the tensile tests showed of samples were stretched; (2) different rates of stretching less deterioration than was expected. However, a close were employed; (3) near break certain stocks seem to yield examination of these tubes showed that they had developed some on shearing. In other words, the rupture is very slow a very poor resistance to tear and were weak when sudden while in other cases it is instantaneous. These curves are tensile stress was applied. For sake of brevity this lack of compared more fully in Table 111. resistance t o sudden stress will be called “shortness.” A shorter and slightly less accurate method of getting the After several attempts to measure this “shortness” property relative energy t o rupture the tongue is to take one-half the without resorting to some new testing machine, the tongue product, S X E/100, where S is the stress a t rupture (kg. per shear test was developed. It is so named because of the sq. cm.) and E is the per cent ultimate elongation. The shape of the test specimen and the effect that is produced. product, the “shear product,” is close enough for ordinary It seems to give about the proper rating to these “short” comparisons and closer to the real energy values than the tubes. tensile product is for the relation that it expresses, because lower concavity factors exist in the shear-stress-strain The Test curves.
V
A specimen like that in Figure 1 is prepared by means of a cutting die, as shown by the pattern in Figure 2. Two parallel marks exactly 1 inch (2.54 cm.) apart are placed on the test piece so that they will be near the middle of the parallel section of its tongue. The sample is then placed in 1 Presented before the Division of Rubber Chemistry at the 76th Meeting of the American Chemical Society, Swampscott, Mass , September 10 to 14, 1928.
Mechanism of Test
The manner of rupture and factors influencing the values obtained were studied to learn, first, what was taking place as the rubber was strained in this sort of specimen, and second, if the test piece was properly proportioned. The rupture always takes place a t the end of the tongue (C-D, Figure 1). A much smaller expenditure of energy is required to start
