INDUSTRIAL AND ENGINEERING CHEMISTRY
168
it was found to decompose into sulfur dioxide and sulfur in the subsequent steam-distillation. Then iron filings were tried, but the ferrous iodide formed also appeared t o decompose in the steam distillation, giving free iodine. Hence, mercury was used instead.) The solution, having been completely decolorized by the mercury, was filtered and the filtrate was steam-distilled after the addition of 2 cc. of sulfuric acid. When all the volatile acid had distilled over, about 5 liters of distillate having been collected, the distillate was neutralized with N sodium hydroxide, using phenolphthalein as indicator. Then 3 cc. of N sodium hydroxide were added in excess and the solution was evaporated down to 200 cc. Now 50 cc. of 5 per cent mercuric chloride solution were added to the clear solution (filtered,if necessary) and boiled for an hour under a reflux condenser (2). The white precipitate was filtered through a Gooch filter, washed with cold water, dried, and weighed. A blank experiment was made taking 1 gram of glacial acetic acid in 600 cc. of N sodium hydroxide and adding 225 cc. of 0.1 N iodine, 27 grams of otassium iodide, 1 liter of water, then 20 cc. of concentrated sulfuric acid diluted to 60 cc. The iodine was decolorized by adding mercury and the rest of the experiment carried out exactly as before. Finally a check experiment was made like the blank, except that the acetic acid contained a known weight of formic acid. The results are given in Table 111.
VOL. 9, NO. 4
from Messinger’s method of analysis it is incorrect. The value 0.00614 should be changed to 0.00598 for the weight of acetone equivalent to 1 cc. of 0.1 N sodium hydroxide. The indicator methyl orange-xylene cyano1 (6) was found to give a very sharp end point in the oxime titration. A small amount of formic acid was detected among the products of Messinger’s iodoform reaction, showing that some of the acetone probably reacts according to the equation CHICOCHI
+ 5NaOH +2CHIs 101 = + HCOONa f 4NaI + 4H20
Literature Cited (1) Ardagh et al., IND. ENQ.CHEM., 16, 1134 (1924).
(2) Brit. Standard Specification No. 576, p. 10, 1934. (3) Cassar, H. A . , I N D . ENG.CHEW,19, 1061 (1927). (4) Goodwin, L. F., J . Am. Chem. SOC.,42,39-41 (1920). (5) Hickman and Linstead, J.Chem. Soc., 121,2502 (1922). (6) Marasco, M., IND. ENQ.CHEM.,18,701 (1926). 7 d ’- /‘’ ‘(7) Pemberton, Card, and Craven, J . S O ~Chem. . Ind., 54, 163T (1935).
RECEIVED November 16, 1936.
TABLE 111. FORMICACID FOUNDIN IODOFORM REACTION PRODUCTS Expt.
Sample Taken Gram
’
1 2 3
0.96
4 5
0.96 MezCO AcOH (blank) 1.0
1.0 1.0
MezCO AcOH (blank) AcOH containing 0 . 0 4 gram HCOOH (cheok)
hlercuric Chloride Ppt.
Formic Acld Found
Gram
Gram
0.045 None 0.331
0 0044
None 0.0323
0.0664 0.0004
0.0064. Negligible
The blank experiments, 2 and 5, show a negligible weight of formic acid, Experiment 3 shows that the method is satisfactory for estimating small amounts of formic in acetic acid. Experiments 1 and 4, though apparently carried out under the same conditions, do not agree very well in the weight of formic acid found, which is low in both cases. I n experiment 4, 0.96 gram of acetone gave 0.0064 gram of formic acid. This would account for an apparent value of 100.6 per cent in the iodoform method for estimating acetone, which is considerably lower than the figure 102.5 actually found. However, the acetic acid found in the steam-distillation was only 80 per cent of the theoretical amount; it may be that both formate and acetate were occluded in the iodoform. The experiments, therefore, support the view that Reaction 2 takes place to some extent. I n applying Messinger’s method to the estimation of methylethyl ketone, Cassar (3) found that constant results of 110.5 per cent were obtained for the ketone under specified conditions. He accounted for this by assuming that two simultaneous reactions occur.
+ + + + +
CHaCHzCOCHs 61 4NaOH = CHI* -t- CH&HzCOONa CHsCHzCOCHs 101 5NaOH =2CHIs CHsCOONa
+ 3NaI 4- 3Ha0
+ 4NaI 4- 4Hz0
The first reaction is the normal one, but the second one also occurs in which more iodine is taken up, thus giving results 10.5 per cent too high; this explanation is analogous t o the one given in this paper to account for the high result of 102.5 per cent obtained in the estimation of pure acetone.
Summary Messinger’s method (4) was found to give results of 102.5 per cent acetone in the estimation of pure samples. Marasco’s oxime method (6) gives results in good agreement with Messinger’s method, but as his factor is obtained
A Modified Mercury Seal for Stirrers LINDSAY H. BRIGGS, Auckland University College, University of New Zealand, Auclrland, New Zealand
T
HE mercury seal for stirrers here described has been found useful in catalytic hydrogenations and oxidations where absorption of gas is measured a t atmospheric pressure. Usually in such reactions stirring must be done with a gastight stirrer or else some system of shaking employed, both of which methods are simplified by use of the present ...J.i...! seal for stirrers, d j , P B In the accompanying fig.... , ure a cross section of the seal ,.. and stirrer is shown. The outer tube, A , is elongated thus enabling a stopper, B, to be slid down the stirrer rod, closing the top of the seal. In order to fill the reaction vessel with the des i r e d g a s , mercury is first a d d e d i n j u s t sufficient quantity to cover the lower end of the tube, C, as shown, and stopper B is slid down to position a. The flask is then evacuated, the air in E bubbling past the mercury without forcing any over. The required gas is then admitted up to atmospheric pressure, which automatically again closes the ends of C , and the stopper is slid up the s t i r r e r rod to position d . More mercury can then be added to the seal to increase the safety margin and the stirrer set in motion. Care must be taken to ensure that mercury is not forced into the reaction flask by a fall in pressure which must be kept approximately a t atmospheric pressure. I
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J.’I I.
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RECFJVED December 10.1936.
