ANALYTICAL CHEMISTRY
1670 The sample and a portion of the extractant are placed in flask A-1 and mixed by swirling. For operations that involve long periods of soaking a t room temperature the apparatus is stoppered with caps C and D. Cold-finger condenser B is used for hot digestion or extractions. The apparatus is heated in eithei a steam bath or heating mantle. To filter and withdraw extract solution the ground drip-tip joint, 9-3, is connected in an upright position t o a three-necked flask or other suitable receiver, which in turn is connected to a source of suction. .Ifter the residual solids are drained, they are dislodged from the surface of the fritted-glass filter disk by s ~ i r l i n gwith a fresh portion of extractant. T o facilitate this operation the vvall of the Buchner-type glass funnel, A-2, should be as short as is conhistent with convenience in sealing the funnel to the flask, -4-1.
P U M P O U T VALVE
INLET PORT
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TO M A S S SPECTROMETER
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1
7;T!
k-(U ! MPS
The apparatus can be built in any size desired. Flasks having capacities of 300 to 3000 ml. have been used in this laboratory for construrtirig the part designated 3-1.
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Figure 1.
A
The principal parts of the unit from which the accompanying figure was drawn to scale were made from glassware items of the following stock sizes: capacity of flask d-1, 2000 ml.; diameter of fritted disk in funnel A-2, 80 mm.: standard-taper through joint A-3, 34/45: outside standard-taper joint A-4, 50/50. These sizes are mentioned here only for the sake of illustration. The relative proportions of the elements of the apparatus can be varied to suit individual requirements. Ruggedness and speed of filtration are favored, however, if the size of A-2 is large rather than small in relation to A-1. Buchner-type glass funnels fitted with L'coarse" fritted disks have been found suitable in constructing this type of apparatus for work with ground plant materials. Removal of spent solids after extraction is facilitated if an oversized joint is used to replace theoriginal flask neck a t A-4.
Sample inlet s>-stem
The sample-loading device is shown in Figure 2. T o load a sample, the two Teflon parts and the split sleeve are neighed. Then the cup is filled with sample. h cup made by drilling a inch deep will hold 5 to 7 mg. of liquid. After So. 50 hole the cup has been filled, it is pressed into the split sleeve, and the blank slug is pressed down on top of it. The assembly is then weighed and the sample ueight found by difference. Xext, the split sleeve is placed in the rere's of the entry port and the pushei shown in Figure 2 is ured t o force the sealing plug and sample cup into the reservoir and force the blank slug into the port to serve as a new vacuum seal. a f t e r a number of samples have been loaded, the reservoir is removed and a clean sphere is substit ut ed.
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Typical Experiment. A 20-gram sample of commercially dehydrated alfalfa meal was defatted by extraction under reflux in a 2000-ml. device of this type. Five 30-minute digestions with separate 450-ml. portions of a mixture of benzene and absolute ethyl alcohol (9 to 1) were made on a steam bath. After each digestion the solvent was removed b y suction and the meal After the \\-:iq rinsed with 50 ml. of the hot solvent mixture. fifth extraction and rinse, air was pulled through the meal until all of the solvent was evaporated. A total of i . 9 % of the neight of the meal was removed by this solvent. The dry, bleached, defatted meal was then extracted tnice \\-ith 80% ethyl alcohol in the same manner as with the benzeneethyl alcohol. With the two extractions, 18.6% of the neight of the original meal was removed.
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Heated Sample Inlet System for Mass Spectrometry V. J. Caldecourt, The Dow Chemical Co., Midland, Mich. EATED
Figure 2.
Sample loader
sample inlet system has been developed to permit
H the loading of weighed amounts of liquids or solids. The solids may be materials volatile at the temperature of the reservoir, or nonvolatile materials that contain volatile components which are to be measured. The system is constructed of glass, Teflon, and stainless steel, and therefore can be used up t o about
250' C. Figure 1 shows the reservoir, loading port, and pump-out valve. The loading port is sealed by a Teflon slug 0.188 inch in diameter and 0.25 inch long. The port was drilled and reamed n i t h a standard-taper pin reamer, so that the diameter a t the top of the port is 0.188 inch. T h e reservoir is a 5-liter sphere fitted with a 1-inch glass pipe joint.
This method of sample loading has proved convenient and useful. It has a limitation, honever, in that a small amount of air is introduced with the slugs. About one half of this seems to be trapped and carried in n i t h the slugs. The other half appear.; to have been disqolved or adsorbed b\ the Teflon, and is released in a few seconds after the slugs are introduced. I n a typical sample, loading 7 mg. of toluene would give a reservoir pressure of about 500 microns in a &liter volume at 200" C. I n the loading process, about 0.003 mg. of air would be introduced. So far, very few samples encountered have reacted with air at this temperature.
