Agitator for Lamp-Method Sulfur Titrations LYLEDOLAN The Texas Company Laboratory, Wilmington, Calif.
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N THE usual procedure for the determination of sulfur in petroleum products by the lamp method (A. S. T. M., D90-30T), it is specified that the carbonate solution in the absorption bulb be agitated during titration by alternately blowing and sucking by mouth on the exit side of the bulb. Considerable pressure is required to force the liquid backward and forward through the packing and, when running a large number of such analyses during a day, this operation becomes rather fatiguing and inefficient, particularly when, as is often the case, the connecting tube becomes partly obstructed by the packing. This tedious and rather unsanitary procedure is obviated by theuse of a simple arrangement, shown in the figure, which has been in continual and successful use in this laboratory for about 14 months. By simple manipulation of the conveniently located three-way stopcock a continuous and uniform agitation may be secured during titration and, when near the end point, the carbonate solution may be transferred rapidly backward and forward between the two bulbs. The orifice shown in the line to the bulb is of the correct size to prevent any reagent being blown from the bulb when the three-way cock is wide open. Where the air pressure supply is high compared to the vacuum obtainable, more uniform operation can be secured by plugging the openings in the three-way cock and drilling suitably small holes to the air and vacuum sides of the cock. RECEIVED Msroh 12, 1934.
A Divided Titration Flask J. W. YOUNG,Glenmore Laboratory, Calgary, Canada
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H E simple and convenient divided-titration stirring r o d r e c e n t l y described by Richardson (3) has been used by the writer for some time. Richardson has p o i n t e d o u t the advantages of speed, accuracy, and convenience offered in titrations. In many cases, particularly in the Kjeldahl nitrogen determination, titration is preferably made in a flask and the stirring rod is inconvenient. The flask here described is a simple device for extending the D~~~~~~T~~~~~~~~F~~~~ method and with slight modification is also suitable for differential electrometric titration. The flask is easily made by sealing a capillary tube between two pieces of glass tubing, and attaching to an Erlenmeyer flask and test tube, as shown in the figure. The apparatus is preferably made of Pyrex, the capillary being about 3 cm. of 0.5-mm. tubing, and the test tube being of about 15 ml. capacity and diameter less than 1 cm. The rubber stopper with stopcock is preferable to a sealed-in stopcock, making the apparatus easier to clean. In operation, the solution t o be titrated is placed in the flask and a portion drawn into the side tube. Titration is made
rapidly until the end point is passed, and part of the solution in the side tube run in. A more careful titration to the end point, with a final rinse of the side tube, completes the titration. With a buret having a time of over 1minute, it is almost impossible to pass the end point, the liquid in the side tube always serving as a reserve and obviating annoying backtitration. With normal swirling for mixing during titration, there is very little disturbance of the liquid in the side tube and it will not splash onto the stopper. The flask can be modified to make a very satisfactory arrangement for differential electrometric titration as described by Cox (1) and modified by MacInnes and Jones (2). A two-holed rubber stopper, carrying stopcock and a glass tube with platinum foil electrode, replaces the stopper and stopcock on the side tube. The second electrode may be placed in the solution through the mouth of the flask but is preferably inserted through a side tube, as shown by dotted lines. This second electrode has a rather narrow strip of foil and is easily attached by slip-on rubber tubing. Mechanical agitation is unnecessary in this titration, swirling by the hand being sufficient for thorough mixing. LITERATURE CITED (1) Cox, J. Am. Chem. Soc., 47, 2138 (1925). (2) MacInnes and Jones, Ibid.,48,2831 (1928). (3) Richardson, Ibid.,55, 2794 (1933). RECEIVED April 20, 1934.
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