ANALYTICAL EDITION
170
tion, which corrects for any error due to capillarity, is found by disconnecting the sample bulb, setting the mercury at a pipet calibration, and using the mercury level in the other tube as a zero mark. The leveling bulb, with a capacity of I50 to 200 cc., is supported by either of tm7o split rings as shown. In the lower position the mercury levels are at B-B-B and the reading of pressure below the barometer, PI, is made when the mercury in the pipet is a t the lower graduation. The leveling bulb is then raised to the other ring, so placed that the upper graduation in the pipet is reached and the levels are at A-A-A. The pressure above the barometer, Pz, is read. The readings are repeated until a t least three checks within 1 mm. are obtained on both upper and lower readings, since at first there is usually a slight creeping of the levels. The use of two rings facilitates ’ the finding of the proper positions. Frequently the ground-glass cover of the sample bulb becomes stuck so tightly that it cannot be pulled out. I n mch cases it can be removed by connecting air or water pressure to the tube. Calculation of Volume
Volume of pipet bulb Volume of sample bulb (empty) Weight of sample Barometer UPPERREADINGS (Ps) 266.7 267.3 267.6 267.3 Mean 2 6 7 . 2
96.04 cc. 123.65 cc. 2 3 . 8 grams 768 mm. LOWERREADINGS (PI) 224.0 224.0 223.0 224.0 223.8
Then, applying Equation 2,
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The true volume of the sample is therefore 123.68 CC. - 106.43 CC. = 17.22 CC. and from this volume and the weight of the sample the true 23.8 density is -17.22 It might be interesting to note that the apparent density as calculated from linear measurements is 0.606. This indicates 56 per cent of voids.
The method was found equally applicable to wet samples provided a correction was applied for vapor pressure of water a t the surrounding room temperature. For wet samples the formula becomes
The calculation is expressed most simply by the equation: Difference in volume - small volume Difference in pressure small pressure
VOl. 1, K O . 3
v=
(1)
B-PI- W p1 P2
8’
+
(3)
where W is the vapor pressure of water. For wet soluble subin which the difference in volume is the calibrated volume of stances this correction should be replaced by the vapor presthe pipet bulb, V’; the difference in pressure is the sum of sure of the saturated solution. The apparatus has been in use for six months and has the two readings on the meter rods, P I Pp; the small pressure is the barometer reading, B, minus the lower reading, P I ; given satisfactory results with such materials as soap, leather, and the small volume is the gas volume, V , in the sample and various powders. It is to be noted that pockets of air within a sample, even if they are enclosed completely, are bulb including the capillary tube. Therefore, compressible. and so are not included in the calculated volume, B - PI V _ _V’ =or V = (2) unless the solid material is rigid. Pi Pz B - Pi pi pz By determining the sample bulb volume empty and subLiterature Cited tracting the volume when it contains the sample the true Chwolson, “Lehrbuch der Physik,” Vol. I, p. 303 (1918). volume of the sample is obtained. With sufficient care (1) (2) Dobrochotow, Z. Hauptanstall Masse Gewichte, 8, 91 (1907). volumes can be estimated with an accuracy of 0.2 or 0.3 cc. (3) Lo Surdo, Nuovo cimento, [ 5 ] 12, 41 (1906). The results obtained on a sample of leather are as follows: (4) Zeleny and McKeehan, Phys. Reo., 30, 189 (1910).
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Bottle for Accurate Weighing of Volatile Liquid Mixtures‘ 2. Blaszkowska POLYTECHNIC HIGH SCHOOL, WARSAW, POLAND
0 WEIGH several liquid components of a mixture in one container is usually a long, difficult task. When weighing one of the liquids following the first it is easy to pour too much, necessitating a new calculation and the addition of new portions of the liquid already weighed. There are still more difficulties when mixing easily volatile liquids, for weighing bottles with capillary tubes and capillary pipets are then necessary and the time of weighing is still longer. During work on esterification, the author designed the apparatus shown in the accompanying figure, which facilitates and shortens the weighing, and is very accurate. It is especially suitable for weighing easily volatile liquids. The apparatus consists of two containers, A of about 100 cc. capacity and B of about 50 cc. capacity, depending on the amount of the liquid to be weighed, joined by the S-shaped tube, C. The small tube D in container A is closed by means of a rubber tube with a glass stopper or by a glass stopper 1
Received February 28, 1929.
directly. Container B has a wellground glass stopper. The first liquid is weighed into B by pouring it through the inlet K; the side tube D must be closed. The liquid partly fills the container B and part of the bent tube C. The liquid can be added or removed with a pipet through K . After the weighing the opening K is closed and the liquid is poured from B to A by inclining the apparatus. The bent tube C must be wide enough (6 to 8 mm.) to allow the simultaneous passing of the liquid from B to A and of the air from A to B. Each of the other liquids is also weighed in the container B. The first por-
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 15, 1929
tions are used for washing the walls of B and C. After pouring these portions of the liquid into A , the remainder is weighed as the first liquid in B. Thus the apparatus allows us to weigh each of the liquids separately. The time of preparation of a mixture is shortened
171
considerably and the hydraulic seal prevents the volatilization of the liquids weighed previously during the weighing. I n order to mix the weighed liquids accurately, it is advisable t o cool the container A and thus to condense the vapors in B and C. The mixture from A is poured out through the side tube D.
Recommended Specifications for Analytical Reagent Chemicals’ Bromine, Cupric Ammonium Chloride, Cupric Oxide Powdered and Granular, Ether, Ether Absolute, Potassium Chromate, Potassium and Sodium Tartrate, Silver Sulfate, Zinc Low in Arsenic, Zinc Low in Lead and Iron W. D. Collins, H. V. Farr, Joseph Rosin, G. C. Spencer, and Edward Wichers COXMITTEE O N AKALTTICAL REAGENTS,AMERICANCHEMICALSOCIETY
T
HE specifications given below are intended to serve for
reagents to be used in careful analytical work. The limits and tests are based on published work, on the experience of members of the committee in the examination of reagent chemicals on the market, and on the studies of the tests made by members of the committee as the various items were considered. Suggestions for improvements of the specifications will be welcomed by the Committee. I n all the directions the acids and ammonium hydroxide referred t o are of full strength unless dilution is specified; dilution 3) means 1 volume of the reagent or strong indicated as (1 solution with 3 volumes of water; “water” means distilled water of a grade suitable for the test described; reagents used in making the tests are supposed to be of the grade recommended below or in previous publications ( 1 , 2, 3, 4, 5 ) * from the committee. Directions for the preparation of the ammonium molybdate solution are given under the test for phosphate in ammonium nitrate ( 3 ) . A time of 5 minutes is t o be allowed for the appearance of precipitates and before observation of color reactions, unless some other time is specified. Blank tests must be made on water and all reagents used in the tests unless the directions provide for elimination of errors due to impurities. Solutions of samples must be filtered for tests in which insoluble matter would interfere.
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Bromine Note-Reagent bromine should be sold in sealed ampouls. The requirements and tests given below apply to such bromine. If distributed in bottles, the reagent may contain organic bromine compounds and a larger quantity of non-volatile matter derived from the material necessarily used in sealing the bottles. REQUIREVENTS
Spec{$c Gravity (limit for chlorine)-To pass test. h’on-Volatile Matter-Sot more than 0.015 per cent. Iodine (1)-To pass test (limit about 0.05 per cent!. Organic Bromine Compounds-To pass test. Sulfur Compounds-Not more than 0.002 per cent as S. TESTS
Specijc Gravity (limit for chlorine)-Shake 6 volumes of the bromine with 1 volume of water, The apparent specific gravity at 26’/25’ C. of the bromine saturated with water should be not Tess than 3.090. This corresponds to a content of about 0.3 per cent chlorine. Non-Volatile Matter-Volatilize 5 cc. in a weighed dish on the steam bath. The weight of the residue should not exceed 0.0025 gram.
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1 Presented in connection with the report of the Committee on Analytical Reagents a t the 77th Meeting of the American Chemical Society, Columbus, Ohio, April 29 to May 3, 1929. Italic numbers in parenthesis refer to previous reports cited a t end of article.
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Iodine-Shake 1 cc. with 50 cc. of water and about 3 grams of granulated zinc until all the bromine is reduced. Filter and add to the filtrate 1 cc. of 10 per cent ferric chloride solution and 5 cc. of chloroform, Shake well. S o pink or violet color should appear. Organic Bromine Compounds-Add 1 cc. of bromine t o 25 cc. of 10 per cent sodium hydroxide solution, dilute with an equal volume of water and allow to stand overnight. No oily drops or film should separate. Sulfur Compounds-Weigh out about 5 cc. of the sample, add 1 cc. of nitric acid, allow to stand one-half hour, and evaporate to dryness on the steam bath. Take up with a few drops of hydrochloric acid and evaporate again t o dryness. Take up in water, make to a volume of about 50 cc., filter, add 1drop of hydrochloric acid, heat t o boiling, add 5 cc. of 10 per cent barium chloride solution, and allow to stand overnight. Filter, wash, and ignite the precipitate. The weight of sulfur (S) calculated from the weight of barium sulfate should not be more than 0.002 per cent of the weight of bromine tested.
Cupric Ammonium Chloride REQUIREMENTS Insoluble Matter-Sot more than 0.005 per cent. Free Acid-To pass test. Nitrate (N0a)-To pass test (limit about 0.01 per cent). more than 0.010 per cent. Sulfate (Sod-Not Substances not Precipitated by Hydrogen Sul.Ade-Sot more than 0.16 per cent. Iron (Fe)-Xot more than 0.005 per cent.
TESTS Insoluble Matter-Dissolve 10 grams in 100 cc. of water and heat on the steam bath for 1 hour. If any insoluble matter is present, filter, wash thoroughly, and dry a t 105’ to 110’ C. The weight of the insoluble residue should not exceed 0.0005 gram. Free Acid-Dissolve 4 grams in 100 CC. of water and add 4 drops of methyl orange indicator. Divide the solution into two equal portions. Upon adding 0.2 cc. of 0.1 N sodium hydroxide to one portion the purplish color should disappear. Nituate-To 2 grams of the salt in 10 cc. of water add 10 cc. of 20 per cent sodium hydroxide solution. Boil to remove all ammonia, and filter. T o the filtrate add 10 cc. of sulfuric acid and 1 drop of indigo solution (1 in 1000). .The blue color should not entirely disappear in 5 minutes. Sulfate-To the filtrate from the test for insoluble matter add 1 cc. of hydrochloric acid, heat to boiling, add 5 cc. of 10 per cent barium chloride solution, and allow to stand overnight. Filter, wash, ignite, and weigh.’ The weight of the barium sulfate should not exceed 0.0025 gram. Substances not Precipitated by Hydrogen Suljde-Dissolve 2 grams in 100 cc. of water, add 1 cc. of sulfuric acid, precipitate the copper with hydrogen sulfide, and filter. Evaporate 50 cc. of the filtrate, ignite, and weigh. The weight of the residue should not exceed 0.0015 gram. Iron-Dissolve the residue obtained in the preceding test by warming with 1 cc. of hydrochlolrc arid, dilute with 28 cc. of water, add 2 cc. of hydrochloric acid and 3 cc. of 10 per cent ammonium thiocyanate solution. Any red color produced should correspond to not more than 0.05 ma. of Fe.
Cupric Oxide, Powdered and Granular REQUIREMENTS Insolable in Arid-Sot more than 0.02 per cent. Carbon Compounds (as C)-Not more than 0.02 per cent.
