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Rapid Filtration and Drying Technique. Raymond H. Pierson, Analytical Chemistry Branch, U. S. Saval Ordnance Test Station, Inyokern, China Lake, Calif. OLUTIOSS
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containing partially hydrolyzed cellulosic solids or
S other gelatinous precipitates are frequently difficult to filter
through ordinary folded filter papers, Gooch crucibles, or sintered glass. A simple apparatus for achieving rapid filtration of such solutions and quantitative washing has been widely used but is often overlooked. Most of these “difficult” solutions will filter e a d y through a paper thimble supported in a filter tube similar to Corning Glass Works item 9480. Moderate suction may be applied if the paper thimble is cushioned with a plug of glass wool. The filtration step is sometimes to be followed by extraction in a Soxhlct with a solvent different from the one employed during filtration. This means evaporation of all the first-used solvent from the paper. Complete removal of water or organic solvents map require 4 hours or even longer by the procedure of drawing air through the asscmbly a t room temperature or by oven drying. Especially in the case of thimbles which contain large cellulosic precipitates, removal of water or even low boiling solvents such as methylene chloiide is very tedious. Thorough drying may be accomplished in half an hour merely by placing the tube on its side in an oven and drawing heated oven air through i t by means of a rubber suction line run into the oven through a small hole and attached to the small cnd of the filter tube. The determination of the oil content of water samples by one of the commonly used procedures may be considered a typical application of the technique described. I n essence the method drpcnds on collecting the oil on precipitated ferric hydroxide, filtr,ring, diying, and extracting with ethyl ether. The oil col1ectc.d in this way from boiling solution is not low-boiling-point niatrrial and may b c l dried by the oven-suction procedure PUBLISHED u i t h t h e permission of F. W. Brown, Technical Director, U. S. S a v a l Ordnance Test Station.
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The rate of draw-up can be adjusted to operate satisfactorily in one of three groups of aluminum concentrations in the alloys: 4% and over, between 4% and 1%, and 1% and below. Initially the draw-up rate is adjusted using water; the proper draw-up times for the three groups are approximately 0.5, 1,and 2 seconds. Final valve adjustments are made when sampling metal, with the object of obtaining solid samples about 7 cm. long. The Magnesium Alloy Plant has guns adjusted for use in each of the three groups. If the rate of draw-up is appreciably less than optimum, a short sample will be obtained which cannot be made into two electrodes and sparked nith convenience. Samples drav n appreciably faster than optimum are usually hollow or porous. The degree of tolerance required in the draw-up rate for each group )vas small enough to prevent successful application of a rubber bulb for drawing the metal. After service, some guns will begin to draw samples shorter than standard, owing to partial plugging of the valves by dirt. To correct these guns it is more convenient to adjust plunger travel to correct sample length than to alter the sensitive valves. Periodically guns are cleaned and reset with water as described. It is believed that this type of gun can be u-ed for sampling alloys of other base metals.
Sampling Gun for Spectrographic Pin Samples. H. €1. Grossman, C. B. Pratt, and W. S. Myers’, Spectroscopy Laboratory. The Dow Chemical Co., Midland, i\Iich. gun for drawing molten magnesium alloys into borosilicate glass tubing for spectrographic pin samples has been in use a t the Magnesium ;illoy Plant, Don- Chemical Co., since June 1946. A cross section of a cocked gun is shown in the diagram.
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Glass Atomizer for Use in Chromatography. W.J. Wingo, Biochemistry Department,, The TTniversityof Texas, 31.D. .biderson Hospital for Cancer Research, Houston, Tex.
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In operation, a piece of tubing bet,ween 5.0 and 5.4 mm. in inside diameter and 20 cm. long is placed in the end of the gun and secured by compressing t,he rubher bushing, B , around it by the thumb nut, A . The sample is drawn into the tubing by dipping it a proximately 0.5 inch into molten metal from which the flux has%een.temporarily cleared, and triggering the gun. The trigger ],eleases the spring-loaded rod, which causes motion of the leather-cup piston, E , thereby creating the partial vacuum for sampling. Initial guii adjustments are made by adjusting length of piston travel by screw F, so that wat’er is drawn into a sampling tube to :I height of 7 zt 0.5 cm. Further adjustments are made by adjusting screw D , which controls rate of draw-up by determining the :mount of clearance around the taper pin, C. During draw-up, air flows from the sampling tube to the cylinder through a small opening formed by this clearance. For a satisfactory sample, the rate of draw-up depends upon the aluminum concentration in the magnesium alloy as well as upon other factors such as temperature of the molten metal. 1
Present address, City Mortgage Co., Rirerside, Calif.
atomizer is often needed in paper chromatoexample, the method of Berry ( 1 ) requires that the chromatogram be sprayed with sodium hypochlorite, and several other methods require the spraying of corrosive agents. Commercially available glass atomizers are rather expensive, and a previously published design ( 2 ) for an atomizer to bc constructed in the laboratory requires a grountiglass joint. r\bout, a year ago, a glass atomizer was built in this laboratory t o use in detection of urea on paper chromatograms by the method of Berry ( 2 ): it performed so well t h a t the author made several of them, arid has since that. time used them in all his chromatographic spraying. I t is easy to make ( a fair amateur glass blower can make one in about half an hour, including the t,ime required for cooling a t several intermediate stages and the t,ime for firial annealing); it delivers a good volume of a spray having a small droplet size, and requires only a few pounds per square inch of air pressure for operation. (An atomizer t,ypical of this design YI ill begin to spray when supplied by air a t 7 pounds per square inch; it works very well a t 10 pounds per square inch, spraying at this pressure about 5 ml. per minute.) sosmn.*LLIc
A graphic analysis-for
1939
