A Constant-Temperature Bath for Stodola's Acetylation Microapparatus HAROLD G. CASSIDY Yale University, New Haien. Conn.
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intermittent attention on the part of the operator to maintain t'his temperature. The apparatus described maintains the required temperature indefinitely without att'ention. This frees the operator. and t'lie use of tn-o reaction flasks allon-s him, while one reaction is in progress, t,o titrate the previous reaction, clean the flask, arid weigh out the sample for the nest react'ion without interruption. Over t'he course of four consecutive analyses as much as 2 hours may thus be saved. The apparatus employs the principle of the Abderhalden dryer, in that the desired temperature is maintained by the vapors of a suitable refluxing liquid (water). The reaction flask of Stodola's apparatus is partially immersed in glycerol in a \?-ell d i i c h is heated by the vapors from the boiling liquid in the large flask, A . The vapors are returned by a short wat'er condenser which is con-. nect'ed in series with, and following, the condenser of Stodola'b apparatus. Glycerol is used in the well because it is very easily washed from the reaction flask before the titration is carried out. Mineral oil is inconvenient' here, because it is hard to wipe it from the reaction flask. Mercury could be used if the laboratory were well ventilated, but i t is not recommended on account of possible danger to the operator. Flask il is conveniently fashioned from a 50-cc. Pyrex Erlenmeyer. The dimensions as shown in the figure are adjusted to suit t'he measurements of the acetylation flask. To use the apparatus a small amount of water is placed in flask A and the condenser water is turned on. The well is filled about t'wo-thirds full of glycerol to assure good thermal contact with the reaction flask, and the water is brought to a boil x i t h a microburner. The apparatus needs no further attention. A litt,le zinc dust in flask d will promote smooth ))oiling. This type of bath is, of course, suitable for other reactions which require a constant temperature over a period of time. FIGURE1. COSLTGT-TEMPER~T~RE BATH (SOLID L r m s ) . ACETYLATIOX Acknowledgments .4PP.4RArrCs I S P L A C E (BROKEN LIKES)
TODOL-A'S method ( 1 ) for the microdeterniination of
hydroxyl and amino groups involves quantitative acetylation of these groups, which ib carried out in a small flask ~r
hi
-1.Flask for water. B . Glycerol in well. C Acetylation flask. Condenser jacket tube E is more conveniently placed a t 90' t o the plane shown, so as t o be out of u a y of acetylation apparatus
The author nishes to acknowledge with thanks the aid given by James Cason and Walton Geiger in developing and testing this device. Literature Cited
fitted with a vertical condenser (shown with broken lines in the diagram). For complete reaction the contents of the flask must be held a t 95" to 100" C. for one hour. This i ordinarily achieved by means of a glycerol bath and it require\
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1 I Stodola, F. H., Mzbrochem2e, 21, 180 (1936)
R E C E I Y E DAIav 3 1938
Courtesy, M . L. Willard
BARIUMCHLORIDE (PHOTONICROGRAPH) 456
