412
’
INDUSTRIAL AND ENGINEERING CHEMISTRY
action of the methanol. These factors \yere verified during 30minute room temperature studies, where t,he ester in methanol solution was added in 2-ml. portions either t o 2 ml. of 2 -V sodium hydroxide in 90% methanol or t o 2 ml. of 2 S aqueous caustic. In the one case this represented essentially alcoholic environment and in the other about a 50% aqueous medium. Results obtained on several esters are given in Table 11. .4 comparison of results from the two reagents definitely proves the beneficial effect of water. In the alcoholic environment saponification was incomplete, even with the simplest esters. In the aqueous alcoholic medium, however! saponification was complete for most of the normal lower esters. tert-Butyl acetate *huffed the first marked evidence of side-chain interference in the
Vol. 16, No. 6
aqueous medium, while methyl-?e-caproate represented the firzt normal ester not completely soluble in the mixture. LITERATURE CITED
(1) Assoc. Official Agr. Chem.. “Official and Tentative Metii(
Analysis”, 5th ed., p . 432 (1940). Bryant and Smith, J . A m . Chem. Soc., 58, 1014 (1936) Caudri, Rec. trav. chim., 4 8 , 4 2 2 (1929). (4) Redeman and Lucas, IND. Esc. CHEY.,ANAL.ED.. 9, 621 (193; (6) Rieman,lbid., 15, 325 (1943). (6) Shaefer and Picard, Ibid., 10, 515 (1938). (7) Smith and Bryant, J . A m . Chem. Soc., 57, 61 (1935) (2) (3)
PRESENTED in part before the Division of Analytical and Micro Chemistr? the 106th Meeting of the .IJIERICAN CRBMICAL SOCIETY, Pittsburgh, Pa.
Modifications of Apparatus for Deuterium O x i d e Determination by the Falling Drop E. S. FETCHER, JR.’,
Department of Physiology, University of Minnesota, Minneapolis, Minn.
-T
HIS note outlines modifications of the apparatus described by Keston, Rittenberg, and Schoenheimer ( 2 ) which permit greater speed of deuterium oxide analysis. Two distillation trains are used (see diagram), the components of which are more readily cleaned and more interchangeable than those of Keston et al. The distillation trains are supported rigidly only a t positions i. Where many determinations arc to be made, the following glassware will be found sufficient: 10 tubes a; 3 each of tubes b and c; 2 each of tubes d and g; 14 plugs e; and 6 weighing bottlesf. Tubes g with weighing bottles can be attached to tube a2 in place of the plug when the sample roiitains no organic material and combustion is unnecessary. Thc. outlet of the combustion furnace is adapted to fit the n tubes. The sample, with barium carbonate, is boiled for a fe\Y moments before the pressure is reduced, to eliminate bumping. (‘alvium oxide is used in tube b in place of potassium hydroxidv and chromic oxide to eliminate replaceable H’. a s condensing medium an ice-saturated calcium chloride bath is convrnient, inexpensive, and entirsly satisfactory.
An accurate, relatively simple, and easy to use micropipet can be made from a microscope mount and a hypodermic syringe; its operation is entirely mechanical. The outlet of a 1-cc. tuherculin syringe is attached rigidly t o one end of an appropriately bent 0.5-mm. capillary: the other end of the capillary is drawn to a small tip. The syringe barrel and capillary are mounted firmly on the coarse-adjustment housing of the microscope mount in such a way that motion of the fine-adjustment housing is not interfered with. h spring is slipped over the lubricated plunger of the syringe before inserted into the harrel. The plunger is actuated by a pre . threaded pin (from an inexpensive micrometer caliper, f ample). The threaded sleeve in nhich this pin turn.. is attached to the fine-adjustment housing. Two stops allow the pin to h(s turned through only part of a revolution. The capillary arid byringe are filled, under vacuum, with mercury. The coarse adjustment of the microscope mount raises and lo~vcrathe entire pipet; the fine adjustment is used for filling and flushing t’he capillary; rotation of the threaded pin through limit,s delivers the droplet. The capillary may be a removable tip for easy cleaning, and with a mer-
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1 Present address, Equipment Laboratmy, Engineering Division. Wright Field, Dayton, Ohio.
tremely vigorom stirring of the constant-temperature bath wndcrs thtx maintrwance of the required constancy relatively such -stirring may be achieved little vibration with the impeller tlcscribed by Hemingv%y and Shelley (I). ;Is a thermoregulator, copper tubing filled n-ith 1 , 2 - d i b r o m o m e t h a n e h a s given excellent results; 1 , 2 - d i b r o m o methane has a low specific heat, high thermal conductivity, and high expan.-ion coefficient, so that it is about tTvire a- effective as the liquids usually used in thermoregulators. Ordinary cements cannot be used with this suhstanw t o attach the copper tube to the glass t h e r m o r e g u l a t o r head; it should be sealed directly to the copper, or the glass tuhing can be inserted into a cup of Wood’s metal surrounding the copper tube. The heater element used 15 enameled copper wire connected to the secondary (10 volts, 12 amperes) of a transformer: this element has almost no heat lag. h mercury, constant-head overflow column is used t o maintain a constant flow of cooling water through the bath. LITERATURE CITED
(1)
Hemingway, Allen, and Shelley. FY.
W.,Rev. Sei. Instruments,
11, 204-5
(1940).
Rittenberg. D., and Schoenheimer, R., J. Biol. (‘hem.,
( 2 ) Keston, A. S.,
122, 227-37 (1942).
