INDUSTRIAL AND ENGINEERING CHEMISTRY
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aluminum shot) to use in them. I n case heavier objects are being weighed, care should be taken to have the vessel and the tare made of the same material, since t,he difference even between quartz and glass is sufficient to introduce appreciable errors in case the vessels are relatively heavy. Though the writer has had no experience in this connection, it appears that the weighing of the absorption tubes used in carbon and hy-
VOL. 8, NO. 3
drogen determinations must be subject to especially large variations when lead shot are used in the tares, because of the relatively heavy objects weighed. The use of weights instead of tares leads to the same needless errors unless the weights have the same density as the objects to be weighed. R E C E I V April ~ D 3, 1938.
New Apparatus for Analytical Laboratories Crucible Support for Desiccators, Graduated Cylinder, and Flask Cover F. E. TUTTLE University of Kentucky, Lexington, Ky.
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S A RULE desiccators are supplied without plate or other device for support of crucibles and, on account of the inflexibility and expense of porcelain plate supports, the time and ingenuity of the user are often consumed in the fabrication of makeshift substitutes of glass, pipestem, etc. The crucible support, Figure 1, described in this article is designed for use in the regular 15-om. (6-inch) Scheibler desiccator and will hold six No. 0 or 00 porcelain crucibles with covers or the same number of platinum crucibles of corresponding sizes.
J
FIGURE1
The support is made of pure nickel wire with all intersections securely brazed. Long and continuous use of the support justifies the following claims: By adjusting the legs it is readily adapted to variations in the shapes of desiccators, is held firmly in position during any legitimate use of the apparatus, holds the crucibles securely, may be deformed slightly to accommodate crucibles of different sizes, allows unrestricted circulation of air, and is kept bright with a minimum expenditure of time and the use of a little fine steel wool. GRADUATED CYLINDER. I n those chemical operations where one has occasion to measure rapidly volumes of liquid reagents, solvents, etc., there is great need of a handy measuring cylinder of moderate capacity, one that is sufficiently accurate, not easily upset, sturdy in construction, and not readily broken. The cylinder illustrated in Figure 2 has all these characteristics and has been used in the different laboratories with great satisfaction, particularly in quantitative analytical work. Whereas the tall, narrow, 100-ml. cylinder in regular use a t present is characterized by great instability, generally resulting in breakage when tipped over unless protected by
some sort of shock absorber, this I, qOn,m 4 short, wide cylinder stands more firmly on the table, is more readily filled and emptied, has two lips for convenient pouring, has never b r o k e n when t i p p e d over, is graduated both up and down, and allows yolumes to be measured as accurately as in any other cylinder of the same diameter. It is not recommended for work that should be done only by an accurately calibrated pipet, buret, or certified tall narrow cylinder, but when made according to the d i m e n s i o n s g i v e n it stands s u p r e m e as a general-purpose , r----------6smM,-------~ mea s u r i n g cylinder of 100-ml. capacity. FLASK C O V E R .Many times, FIGURE2 p a r t i c u l a r l y when c o r r o s i v e liquids are being boiled in flasks, it is desirable to resort to some device for control of spattering, evaporation, prevention of free access of air, dust, etc. I n the past small funnels, inverted porcelain crucible covers, and glass bulbs have been employed for this purpose and generally with unpleasant results, because the center of gravity of the miscellaneo covers is above the rim of the vessel being covered. The cover as illustrated (Figure 3) is designed upon a new
FIGURE3
MAY 15, 1936
ANALYTICAL EDITION
principle which places nearly its entire weight inside and below the rim of the vessel, so that it will remain securely in position even while the flask is being shaken. Thus far three sizes of this cover have been successfully used and a careful inspection of the cut of the No. 3 size singly and in cross section as closing a 300-ml. Pyrex Erlenmeyer flask will show that it is capable of being used upon a wide
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range of flask sizes-e. g., No. 1 may be used to close orifices from 11 to 19 mm. diameter, No. 2 those from 16 to 29 mm., and No. 3 those from 21 to 39 mm. Other sizes may be made if desirable. The apparatus described in this article may be secured from Eimer & Amend, New York, N. Y. RECEIVED March 19, 1936.
Condenser System for Fractional Distillation ELDON A. MEANS AND EDWARD L. NEWMAN, The Eldon A. Means Co., Wichita, Kans.
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HE condenser described here .has the advantages of flexibility and greater efficiency over the conventional types, being better insulated and providing an arrangement whereby almost any cooling medium may be used. The illustrated apparatus has given great satisfaction in condensing vapors from fractional distillations. It greatly resembles the top of a Podbielniak column (8). An evacuated glass jacket, silvered for efficient heat insulation, surrounds the bwet and condenser. The condenser itself is a metal cylinder fitting into the top of the glass jacket and is insulated from the glriss by means of an asbestos cord. The cooling medium is run down into the condenser through tube A and escapes at D. Compressed carbon dioxide is very satisfactory, although liquid air or water may be used, according t o the condensing range. The inner tube or condensingtube is of metal and contains a spiral strip extending down t o the buret and dividing the tube into two compartmients. Thus the vapors coming in at B pass down one side of the tube, condense, and fall into the buret. Displaced air must pass up the other side of the dividing strip and emerge at C, losing condensable vapors in transit. The metal condenser tube is connected t o the glass buret by soldering to the platinized glass ( I ) . This provides an air-tight seal between the metal and glass. Thiis apparatus is particularly useful in the distillation of gasoline. Lighter fractions and gases can be condensed by
use of a low-temperature cooling medium such as c a r b o n dioxide or liquid air. The condenser is well adapted to vacuum distillation, the vacuum connection being made a t C and liquid extracted a t E b y a n y of t h e conventional methods for extraction of liquids during vacuum distillation.
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Literature Cited (1) Frary, Taylor, and Edwards, “ L a b o r a t o r y Glass Blowing,” p. 97, New York, McGraw-Hill Book Co., 1928. (2) P o d b i e l n i a k , IND.ENG. CREW,Anal. Ed., 3, 177
(1931). RECEIVED March 9, 1936,
Dithizone as a Reagent for Dissolving and Determining Spray Residue Lead WAYNE E. WHITE, Western Reserve University, Cleveland, Ohio
T
H E readiness wjt,h which dithizone fdiphenylthiocarba-
zone) reacts with minute amounts of lead even when the lead is in such insoluble compounds as the sulfate and arsenate leads to the thought that this reagent might be made to assume a dual role in the analysis of spray residues for lead. The reagent might serve as the solvent for the removal of the lead from the analyzed fruits as well as in its ordinary capacity as colorimetric reagent. Were this possibility borne out by experimental investigation, and were there no other complicating factors, we should have an analytical method superior to any of those in present use in respect to speed and simplicity (1, 2). After considerable investigation of this problem the writer desireri to announce the following results and conclusions : 1. Lead is dissolved from the surface of fruits by a solution of dithizone in chloroform in the presence of an aqueous solution of potassium cyanide, ammonia, and citric acid. I n order to effect a rapid and complete removal, a number of wa&ings (two to six. depending on the amount of lead and tQb tenacity with which it is held) are necessary. 2. The dithizone color change due to the presence of lead occurs just as in the ordinary procedures. The contact with
the organic matter of the fruit skins does not seem to affect the reagent. As in other dithizone methods of spray residue analysis, there are no probable contaminants which will interfere in the lead determination. An occasional turbidity due to undissolved, suspended matter does not appear to be particularly detrimental to a close comparison of colors. 3. The multiple washings prevent the expected economy of time and materials and may decrease the accuracy and precision of a determination. Further work may reveal a way of increasing the solvent power of the dithizone solution and thereby the most serious obstacle to the success of thia direct method of spray residue analysis will be removed.
Literature Cited (1) Wichmann, H.J., e t al., J . Assoc. Ofic$dAgr. C h . ,17, 130-6 (1934). (2) Winter, 0.B., Robinson, H. M., Lamb, F. W., and Miller, E. J., IND. ENG.CHEM., Anal Ed., 7,265-71 (1935). I ~ E C E IDecember V ~ D 2, 1935. A more detailed discussion of the applioation of this method was presented under the title “A Field Method for the Estimation of Lead as Spray Residue” before the Division of Food and Agricultural Chemistry a t the 90th Meeting of the American Chemical Society, Ban Francisco, Calif., August 19 to 23, 1935.
