DECEMBER 15, 1938
ANALYTICAL EDITION
Results In tests on specially prepared carbon tetrachloride solvates (Table I), the method gave values for purity about 2 per cent higher than those by the older alcohol recovery test. Since the alcohol recovery test as used in this laboratory is known to give results about 1 per cent lower than the correct value (1). the titration method appears t o be at least as accurate. TABLE 11. ROTESOSEIN ROOTSAMPLES AS DETERMINED B Y THE GRAVIMETRIC AND THE VOLUMETRIC METHODS
Koot
Derris
Cube Tirnbo
Sample NO.
Gravimetric Method
%
%
3002 3006 3126 3307 3004 3005 3230
2.0 3.6
2.2, 2.0, 2.0 4 . 0 , 3 . 9 , 3.8 5.8,5.7 7.2,7.4 2.9, 2 . 9 5.6, 5.6 3 8,3 8
5.8
7.4 2.9 5.6 3 9
Volumetric Method
Results of rotenone determinations on samples of powdered root were in good agreement with those by the older gravimetric procedure (Table 11). The precision of the method, as judged by the replicate determinations (Tables I and 11), appears to be as good as that of the gravimetric procedure.
585
Adaptation as a Direct Method Attempts were made to precipitate the acid solvate froni a dichloroacetic acid solution of whole derris and cube extracts. Such a procedure would greatly shorten the determination of rotenone. However, the resinous material formed was difficult t o filter and retained excess acid which it was practically impossible to remove entirely. Xumerous materials were added to overcome this, but none was satisfactory. Naphthalene was the best of such materials tried, and in one sample gave fair but not consistent results. When samples of higher nonrotenone-resin content were tried, the results were again too high. It is possible that future work will reveal a method for applying this idea directly to whole extracts, but no such procedure can be recommended at present.
Literature Cited (1) Jones, H. A., IND. ENQ. CHEM.,Anal. E d , 9, 206-10 1937) (2) Jones, H . A., J. Am. (hem. Soc., 53, 2 7 3 8 4 1 (1931). (3) Jones, H. A., and Graham, J J T J -4ssoc 0 f i c ~ a . ldgr Chem
21, 148-51 (1938). RECEWFOD .4ugust 13, 1936.
A Simple Melting Point Outfit J E S S E W E R X E R , Columbia University, N e w York, N. Y .
I
S ORGANIC laboratory technique, it is common to take
melting points in a beaker while stirring the heated liquid. The outfit herein described is a modification of this wellknown procedure. To make for permanence of setup, greater ease of manipulation, decreased dangers of breakage, and no contamination with rubber, a piece of 4-mm. Pyrex tubing is sealed onto a 400-cc. beaker, as shown in Figure 1. With some care and practice, it is a very simple matter to seal the tube onto the beaker without blowing. T h e t u b e is sealed on a t an angle slightly less than 45 degrees to the vertical and is tilted slightly forward, as shown in Figure 2. This slight forward t i l t makes c e r t a i n that the capillaries will be held in place by being gently wedged in between the thermometer bulb, the bottom of the side arm, and the top of the side arm, and does away with using wire springs or c o n s t r i c t in g the bottom of the side tube. This method FIGURE1
also allows several capillaries to be placed one on t o p of t h e other. so that several melting points can be taken a t one time with only one side tube. h small electric motor is advantageous, as it gives rapid agitation and is noiseless and inexpeneive. Both flywheel and centrifugal stirrers have been used satisfactorily with this type of outfit. For uniform heating, the beaker is supported on a sheet of asbestos. C o t t o n s e e d oil has FIGCRE2 been found very useful as a liquid for the bath. It is compounded with 1 per cent of hydroquinone as recommended by Gill and Ebersole (1) and further protected from dirt and rapid decomposition a t relatively high temperatures by covering the beaker with a thick sheet of asbestos having two small holes bored for the thermometer and stirrer.
Literature Cited ,1' Gill and Eberjole, IND. ENO.CHEV, 23, 1304 119311 R E C E I V EAugust D 18 1938.
