January 15, 1932
.INDUSTRIAL AND ENGINEERING CHEMISTRY
The reproducibility of results by the proposed method is illustrated by the following tabulation, obtained by two different operators burning the same type of gas a t approximately the same rate on two similar equipments: hPARATUB
A B
SULFURFOUND 9 . 7 graina/100 cu. it. 9.6 grains/100 cu. ft.
In the case of most of the synthetic mixtures, a hydrocarbon was used as the diluent for the sulfur compound. To demonstrate that the method is applicable to gases of low B. t. u. value, several synthetic samples were burned using hydrogen as the diluent. It is apparent from Table I that equal reliability was obtained for the range of B. t. u. value of the gases investigated. TABLE11. SUMMARY OF ACCURACY DATA CARBON ETHYL THIO-
Substanoe burned D I s U L P I D E SULFIDE PHENE MEAN’ 2 2 3 7 Number of runs 0 03 0.05 0.06 Maximum error, % 0.07 0.00 0.01 0.04 0.01 Minimum error, % 5.4 3.4 3 9 Maximum deviation, % 2.2 1.7 1 3 00 09 Minimum deviation, % 0 04 0 02 0.03 Mean error % 0.06 Mean deviitition, % 2.0 3 4 17 2 4 0 Baaed upon t h e aeighted average of the three previous columna.
Analysis of sulfur by the method described requires from 1 to 100 liters of gas. Combustion may be completed in 1 to 4 hours, and the sulfur in the absorbent medium is de-
termined gravimetrically as barium sulfate. The improvements which the proposed method offers over the previously suggested modifications of the original Drehschmidt method ( 3 ) , in particular that of the Bureau of Standards, may be enumerated as follows: 1. Demonstrated accuracy and reliability on the basis of the analysis of gases of known organic sulfur content.
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2. Elimination of rubber and cork stoppers, wax, and de Khotinsky cement by the use of all Pyrex-glass construction with ground-glass joints, stoppers, and stopcocks. 3. Addition of a condenser to cool the products of combustion, thereby increasing the efficiency of their absorption by the absorption solution. 4. Use of platinum-to-glass sealed leads for the spark gap, instead of copper- or nickel-platinum leads, eliminating the reaction of the sulfur dioxide with the copper or nickel. 5. Use of a spherical combustion chamber to prevent impingement of the flame and subsequent collapse of the glass walls. 6. Entering of gases into the apparatus at pressures above atmospheric and thus eliminating suction required in other methods. 7. Use of pure oxygen and nitrogen instead of air for the combustion, thus eliminating possible contamination of gas burned with sulfur that may be present in the air. 8. Elimination of dangers due t o explosions. 9. Adaptability of the method to gases over a considerable range of B. t. u. value. 10. Use of burner constructed of Pyrex sealed directly to and being a part of the combustion chamber, thereby eliminating quartz or porcelain. Since the latter required rubber seals, this source of contamination is obviated. The Pyrex burning tube has shown no tendency to melt and close up after being in use for several months. In fact, a crystalline ring of silicon dioxide forms at the tip and is heat-resistant.
In the procedure described, the sulfur is determined gravimetrically as barium sulfate. When the sulfur content of gas is high, the sulfur may be determined with sufficient accuracy by iodine titration of the collected washings or by means of a turbidimeter. These methods, however, have not been found satisfactory when the sulfur content of the gas is less than 2 and 3 grains per 100 cubic feet.
LITERATURE CITED Standards, Circ. 48, 129 (1910). (2) Dennis and Nichols, “Gas Analysis,” p. 351. Maomillan, 1929. (3) Drehschmidt, Chem-Ztg., 11, 1382 (1887), (1) Bur.
RECEIVED August 26, 1931.
A Bicycle-Chain Stirrer S. B. LIPPIKCOTT, Purdue University, Lafayette Ind.‘ STIRRER has been devised which will lie close to the wall of a flask and when turned will scrape the wall clean. It is made from a short piece of ordinary bicycle chain. A hole is drilled through the middle link and an iron rod is chosen which just fits into the link. A hole similar to the one in the link is drilled through the rod near one end. The chain is fastened to the rod with a small pin in such a way that it can be inserted into the flask so that the smooth side of the chain lies against the glass. The rod may be passed through a mercury seal if so desired. The advantages of such a stirrer are: (1) that it can be inserted and removed from the flask very easily; (2) that it fits perfectly the wall of the flask whether with round or flat bottom; (3) that it can be used (within limits) in different sized flasks without varying the length of the chain, since in small flasks the extra links simply double back; and (4) that it functions smoothly even though the rod is out of line with respect t o the axis of the flask. It is recommended for use in any case where it is desired to keep a solid worked free from the wall of a flask and an
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ordinary stirrer fails to do so. Of c o u r s e , it cannot be used in cases where iron will interf e r e w i t h the desired reaction. The author has used it successfully in a vaporphase reaction between magn e s i u m and chlorobenzene in the absence of a solvent. RECEIVED October
1 Present
address. University of New Mexioo, .4lbuquerque, N. M.
23, 1931.
A BICYCLE-CHAIN STIRRER
