786
XOTES
shape and the ends introduced into the glass tubes. These are then gently heated until the wax melts. T h e ends of the steel wire should reach down 3s far as possible into the glass tubes to insure strength. I v A R HOEL.
G R ~ SL~L II, T.J. ?eb I c t h 197'.
A Rapid Mefhod j o y the Esfiwation OJ Acetone. - I n order to be able to estimate rapidly the acetone content of the distillate from crude wood naphtha during rectification, the author h a s adapted the well-known Messinger method (BPY,,21, 3365 ; see also Kebler, This Journal, 19, 316 ( r S g 7 ) , ) so that the burette readings give the number of granis of acetone in IOO cc. (sonietinies expressed as per cent.) directl?.. Procedzc~e.- - P u t I O C . C . of 2N sodium hydroxide solution into a widemouth glass-stoppered bottle, then add exactly I C.C. of the alcohol to be examined, shaking ; iiext add 50 C . C . of the standard iodine solution n~liileshaking ; after three minutes acidify with dilute sulphuric acid (use about 2 3 H,SO,) ; now add starch indicator and titrate hack with standard thiosulphate solution. T h e nuniber of cubic centinieters of iodine solution used by the acetone gives the number of grams of the latter in I O O c. c. For the back titration the writer uses a burette graduated from o to 50 c. c. in I:,", beginning at the bottom ; after titratioii, t h e burette reading gives grams of acetone in IOO C . C . directly, avoiding a subtraction of the reading from j o . I n accordance with the equation :
+ +
+
-+
+
(CH,),CO 31, 4KOH =CHI, K (C,H,O,) 3KI 3H,O. o.oIg of acetone requires 0.1312 g. of iodine. A standard iodine solution is, accordingly, prepared to contain 131.2 g . of iodine in one liter ; the standard thiosulphate solution is prepared of equivalent strength. This method is intended for spirits in which the acetone is high, but does not exceed jo %. I n cases where the acetone does not run over 2 j "/o a 2 j C.C. burette, graduated from the bottom, should be used for t h e thiosulphate solution, and of course only 2 5 C.C. of the iodine solution are used. For solution containing j % or less of acetone, I O C.C. of the sample may be taken, using the 50 C.C. burette ; readings in this case are 0. I % for each C.C. iodine used. ALBERT P.SY. U X I \ ~ E I < S I TO. ~ F BUFFALO.
The fesf forforvzaldehyde in milk by Leach's modz3cafion of the hydrochloric acid a n d ferric chloride fesf.-Recently the government inspector took some samples of milk from our house and had them examined by the government pure food chemist. €le reported that he found formaldehyde in the milk. We tested some of t h e milk from the same source ( b u t not the same lot) and found no formaldehyde. Later he reported
