trainer, once the former's boiling point is reached; the violence of this boilovrr can force the contents out of the top of the condenser. This can lead to a fire if the overflow reaches the burner. The whole apparatus has to be practically dismant'led to charge a new sample into the boiler flask. In many laboratories, where a new charge of entrainer is used for each determination, considerable quant'ities of spent entrainer accumulate and must be recovered. Even though this avoids bumping and boiling over during the determination, the charge to be recovered can boil over near the elid of the distillation when most of the entrainer has been removtd, n s cwnditions s i n i i h t o those described above will then prevail.
Modified Vigreux Column. .-\ustin C. F. Mason, Sout'hern Regional Research Laboratory. Sew Orleans, La. HES
the usual Vigreux apparatus is employed in the
1013-
IV pressure distillation of high-boiling liquids such as nwthyl ricinoleate or the triesters of aconitic or tricarballylic acids. flooding occurs a t the standard-taper connection bet\veen the column a,nd the still pot. The plug of reflux liquid a t the connection permits entrainment of the liquid by the vapor and increases the head pressure in the column. This effect is undesirable at pressures of 20 to 100 microns, as an increase beyond this range result,s in overheating and possihle decomposition of the charge in the still pot.
To o v c i ~ c o mthrse ~ difficulties. ari,:uiyenicwts have t ) ( ~ i (lei scrihed in \\-hic.h the sample is in contact only ivith the entrainer vapor5 ( I , 4). 'lhese modifications, howcvrr, are of rather limited application, as the sample must remain solid throughout the determination, must not be solukde in the entrainer, and must not be sufficiently fine to fall through the interstices of the 1)aqket used for suspending it above the boiling entrainer.
n
An improved adapter has heen designed and constructed ironi borosilicate glass tubing using Quickfit and quartz standard joints. It fit,: between the flask containing the entrainer and thr Dean and Stark trap. The large stopper used for closing the top permits the removal of the dehydrated sample to introduce R new charge as soon as the entrainer has stopped boiling. Tlie test tube used as a sample holder is slightly modified by omitting the usual flared top. A short distance below the top edge of the test tube a hole is made, connected with the edge by a shallow groove. This groove will act as a visual guide t o the wire hook, a, which is used to remove and charge the sample holder. The hole also serves to suspend the test tube during weighing. T o support the sample holder a piece of stainless steel gauze is pushed from the top of the adapter into the ground B34 cone at the other end. The wire netting is first prepared as shown, b. Once it is in place, no further attention is required during the life of the adapter. The gauze will also protect t,he adapter and the boiler flask, should the test tube be dropped accidentally inside the apparatus. Just above the outlet leading to the Dean and Stark trap, five spacing dimples are provided to prevent the tor, edge of the test tube ffom Touching the nall of the adapter Other)?~ s e the , refluxing entrainer would run into the sample holder and gindually remove all its contents. The clearance between the test tube and the inner wall of the adapter (see dram ing i 1' sufficient to avoid chohing by refluxing entrainer above 12" C. I n draftr poqitions lagging with :tqbeStos paper ~ 1 1 1be helpful. The side arm leading to the Dean and Stark trap must be blown on a? near to the B34 cup nq possible, to avoid a pocket which is only inizdqquately swept by entrainer vapors.
nlodified Vigreux C o l u m n Alembic reflux r e t m n Inverted teats C'. Thermometpr well w i t h sintered-glass
.4.
B.
SIII~SCC
To :tvoid this difficulty without increasing the dianirtrr of thr column, an alembic return was incorporated bvhich collected the reflus and bypassed it to the still pot, thus preventing flooding a t the base of the column. The two lower bands of teats of the Vigreux column were inverted to direct droplets of liquid to the side wall and the alembic return. The outer surface of the h glass thermometei, well in thc still pot \vas coated ~ i t sintc>wd to promote hoiling. Improved Dean and Stark Moisture Determination Apparatus. A . IT. Billitzer, 27 Tynte St., North ildelaide, South .-\ustralia.
u
THE
determination of moisture by solvent distillation, various
1-types of trap have been designed for collecting the water i n the distillat,e. The Dean and Stark trap (2, 3 ) has found wide acceptance, but certain difficulties are encountered with the standard setup.
Because the sample is in contact only with e n t r a i n e r v a p o r s the clinging, oily film which impedes reading of collected water is absent.
Bumping and boiling over owur if a number of samples are treated successively in the same charge of entrainer. -1 point is reached where ,so much solid has accumulated that the whole contents of the boiler flask approach the consistency of a paste, when cold. The water contained in the sample to be treated last will. under these conditions, cau:e a violent ,-urge of the en-
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