ANALYTICAL CHEMISTRY
924
of the red d) e is half n-ay down the column. Evaporate the solvent on a steam bat8h. Place another 1 2 5 - d . Erlenmeyer flask under the column and collect solvent until the first tinge of pink appears in the flask. Evaporate the solvent. This flask contains almost all of the aldrin and sulfur, if sulfur is present. Place another flask (weighed) under the column to collect all of the red dye. This flask will collect all of the DDT. (Wash off the tip of the column into the flask.) Evaporate the solvent and dry the residue. Place a 10-ml. graduate under the column as the last of the red leaves the column. Collect 10-ml. fractions until white crystalline solid appears after evaporation of the solvent. This white crystalline material is dieldrin. At this point, place another weighed 125-ml. flask under the column and collect all of the solvent up to the blue dye. Add any crystalline material collected in the 10-ml. fractions after the red t o this flask, using a small amount of mobile solvent to transfer. Dieldrin crystallizes in much the same manner as y-benzene hexachloride and does not require much drying, a few minutes under suction a t 60’ C. being ample. DISCUSSION
Sulfur is often present in aldrin. in the following manner.
The sulfur may be removed
Evaporate all of the solvent on the steam bath and while still hot, allow the molten sulfur to roll into a ball. Evaporate the last trace of solvent with a current of air. -4fter the flask cools and the sulfur crystallizes, carefully wash the aldrin into a weighed flask with mobile solvent. T h e crystalline sulfur will not redissolve, Evaporate the solvent. Since aldrin is somewhat volatile, prolonged heating and vacuum should not be used. -4fter
the solvent has been evaporated, add a small amount of Skellysolve F and then evaporate under suction without additional heat. This aids in the crystallization by removing any nitromethane left by the mobile solvent. This also may be used in the crystallization of DDT. Another aid to crystallization of DDT, after the Skellysolve F has been added, is to swirl the flask as suction is applied. This spreads the D D T so that it will dry faster. Spattering was eliminated by using a steam bath to evaporate the solvent from the flasks. Allowing the solvent to distill greatly increases the speed of the over-all operation. ACKNOWLEDGMENT
The author wishes to express appreciation to H. V. Claborn, U. S. Department of Agriculture, Bureau of Entomology and Plant Quarantine, Kerrville, Tex., for helpful suggestions. LITERATURE CITED
(1) Aepli, 0. T., Rlunter, P. 9., and Gall, J. F., ANAL.CHEJI.,20,
610 (1948). (2) Bur. Entomology and Plant Quarantine, U9D.A Release, “Aldrln, a Coined Name for an Insecticidal Product Containing 1,2.3,-
4,10,10-Hexachloro- 1,4,4a,5,8,8a- hexahydro - 1,4,5,8- dimethanonaphthalene,” Dec. 12.1949. (3) Ibid., “Dieldrin, a Coined Name for an Insecticidal Product Containing 1,2,3,4,10,10-Hexachloro - 6,7 -epoxy- 1,4,4a,5,6,7,8,Saoctahydro-l,4,5,8-dimethanonaphthalene.” (4) Harris, T. H., J . Assoc. Ofic.Agr. Chemists, 32, 684 (1949). (5) Ramsey, R. L., and Patterson, W. I., Ibid., 29, 337 (1946). RECEITED for rei iew April 10, 1952.
hccepted February 15, 1954.
Determination of Isopropyl Alcohol in Dextran and Dextran Solutions GIN0 JOSEPH FRISONE’ Lehigh University, Bethlehem, f a .
I
S T H E course of the preparation of dextran it became ap-
parent that a method for the determination of isopropyl alcohol in the final product \vas necessary. It was also necessary that a rapid and accurate method be developed for control work. The method proposed is suit,able both for routine analysis and for research. This method is a modification of the dichromak oxidation reported by Kemal (1, 2 ) and modified by Stanley (3-6). The pre.sent modification decreases the time per determination and is applicable to milligram quantit,ies of isopropyl alcohol. Previous dichromate oxidations required considerable time, thereby prohibiting their use as control analysis. By varying the concentration of sulfuric acid and of the potascium dichromate it was found that a solution of 0.1 gram of potassium dichroniate in 1.0 ml. of 20% sulfuric acid was sufficient to give rapid and quantitative oxidation of isopropyl alcohol to acetone within 5 minute? on a boiling water bath. The excess dichromate was then removed by adding sodium hydroxide, and t.he acetone was distilled int,o hypoiodite solution. The excess iodine then remaining was titrated with standard thiosulfate a.nd the percentage of isopropyl alcohol calculated. Since the accuracy of this method was dependent on both the primary distillation of the isopropyl alcohol from the dextran solution and the secondary distillation of the acetone from the oxidation solution, it was necessary to determine the completene98 of the dist,illation. I t was known that a distillation is never 100% complete, but the results obtained with the above method indicate that the distillation !vas_ better than 98% complete. The secondary distillation \vas also satisfact,ory as shown :
Present address, Central Research Laboratory, d t l a s Powder Co.,
Y e w Castle, Del.
by the fact that, when two successive 60-ml. fractions of distillate were allowed to pass into h?-poiodite solution, it was found by analysis that all of the acetone was recovered in the first fraction. REAGE\TS
0.01.Y iodine. 0.01S sodium thiosulfate. Starch indicator solution. 48y0sodium hydroxide. 1.1-sodium hydroxide. 6 S hydrochloric acid. Sulfuric acid-potassium dichromate solution. PROCEDURE
ilrrange an entrainment separator, packed column (2.5 X 30 cm.), glass beads, West condenser, and delivery tip into a permanent fractionating column. Use a Liebig condenser as a reflux condenser above the water bath to prevent the escape of the oxidation product. Prepare the oxidizing solution by adding 50 grams of reagent grade potassium dichromate t o 500 ml. of 20% sulfuric acid (aqueous). Weigh approximately 10 grams of dry dextran powder on an analytical balance and record the weight to the nearest 1 mg. (The weighing must be done rapidly. as dextran is slightly hygroscopic.) Transfer the powder t o a 1-liter round-bottomed flask and add 200 ml. of distilled water. Connect the flask t o the fractionating column and distill 100 ml. directly into a 250-ml. round-bottomed flask. Wash the condenser down with two 10ml. portions of distilled water. Remove the receiver containing the distillate and pipet into the receiver 25 ml. of the oxidizing solution. Connect the 250-ml. round-bottomed flask to the Liebig condenser and then immerse the flask in the boiling water bath for 5 minutes. At the end of this period add through the top of the Liebig condenser 25 ml. of cold water and enough 48% sodium hydroxide to change the orange dichromate to the green chromate. The color change is
925
V O L U M E 2 6 , NO. 5, M A Y 1 9 5 4 very distinct. Add only enough caustic to produce the color change. Wash the Liebig condenser with small portions of water to remove the adhering caustic. Transfer the 250-ml. flask to the fractionating column and heat the contents to boiling. Prepare the hypoiodite solution by adding 20 ml. of 0.01N iodine solution and 30 ml. of 1N sodium hydroxide to a 250-ml. Erlenmeyer flask. Connect this flask to the delivery tip of the column and collect 60 to 75 ml. of distillate. The first 10 or 15 drops of the distillate will produce an immediate precipitation of iodiform if acetone is present in the distillate. At the end of the distillation wash the condenser with small portions of water and remove the flask from the fractionating system. Add to the flask sufficient 6N hydrochloric acid to make the solution definitely acidic (usually 6 t o 10 ml.). Titrate the eycess iodine with 0.01.V sodium thiosulfate, using starch indicator. The procedure for the 6% dextran solution is the same, except that 100 ml. of dextran solution and 100 ml. of water are used instead of 10 grams of dextran and 200 ml. of water.
Table I.
The results obtained on a sample of dry powdered destrnn (obtained from R. K. Laros Co.) are summarized in Table 11. A sample of clinical dextran was next subjected to the above analysis and the results are shown in Table 111.
Table 111. Determination of Isopropyl Alcohol i n Clinical Dextran Isopropyl Alcohol, Bfg. Isopropyl per 100 M I . .Ilcohol, % 0 0624 0.0010 0.0005 0 0336 0.0072 0.4320 0.0054 0 3266 100 0.0056 100 0 3379 0.0020 0 1195 100 0.0026 0 1344 100 a Samples 1 a n d 3 of R u n 2 were taken from a different batch from sampler 1 2 3 4, a n d 8 of R u n 4. T h e variation between the samples of a run is due t h diffkient operating conditions in the production plant. Sampie*
Dextran Content, Gram
Sample,
MI. 100 100 100
Determination of Known Concentrations of Isopropyl ilcohol in Water Isopropyl Alcohol, Alp. Added Reco\ ered
8 37 8 37
8 26 8 26 4 85 4 96 4 90 1.2 24
4 91
4 91 4 91 12 27
5
Error 1 31 1 31
1 22 1 00 0 20 0 24
Table 11. Determiriation of Isopropyl Alcohol i n Dry Dextran Powder Run 1
2 3 45
2:
Sample Sue. Grains 10 000 10 000 10.000 10 000 5 000 5 000
Isopropyl Alcohol Found, hlg. 5.94 5.90 5.42 6.10 2 80 2.59
Isopropyl Alcohol, S 0.059 0.059 0.054
coscLusIo3s The approximate time per determination including distillations and titration is 45 minutes as compared t,o a maximum of 12 hours by previous determination ( 2 ) . It is possible to reduce this time by about one half if tLvo fractionating columns are used simultaneously. One column should be used for the distillation of isopropyl alcohol from the dextran solut,ion and the other column for the distillation of the acetone into hypoiodite s o h tion. The experimental results sho\v that this method is applicable both to the determination of subniilligrani quantities of isopropyl alcohol in the final product and to milligram quantities of isopropyl alcohol in the intermediate products.
0.061
0.056 0.052
Using 2,4-dinitrophenylhydrazine to determine if there a e r e any volatile aldehyde or ketone which might cause erroneous resrilts. b Sample analyzed after 3 hours in the vacuum oven set a t 87' C . and 2.5 nim. of mercury. c Sample analyzed after 21 hour3 in the T-aciiiim oven set a t 87' C . and 23 iiini. of mercury.
ACKYOWLEDG.)IEST
The author wishes to express his sincerest thanks and appreciation to George 0. Rudkin, Jr., Chemical Division, R . K. Laros Co., Bethlehem, Pa., under whose sponsorship this work was brought to a successful end, and to \-. B. Fish, Louis M a w , and E. J. Serfass for their cooperation and advice. LITERhTURE CITED
RESULTS
The precieion and aecuracy of this method were checked by using known concentrations of isopropyl alcohol in water solutions Table I summarizes the results obtained. The average error is less than l % , which is equivalent to =kt006 mg. of isopropyl alcohol in a 6-nig. sample.
Chemish. Washington. D. C . , "JIethoda o i d I l a l y S i 3 , " 6th ed., p. 389, 1945. (2) Kemal, H., Z.a w l . Chem.. 107, 13s-4 (1938). . 594 (1939). (3) Stanley, R . D.. J . Assoc. Ofic. d g r . C h e n i i s t ~22. (1) ;Issoc. Offic. -1gr.
(4) Ihid.. 23,576 (1940). (5) Ibid.. 25, 893 ( 1 9 4 2 ) .
R E ~ L I V EforD rcvicu Augiist 2 6 , 1953. .4crepted February 11. 1951
Semimicrodetermination of Acetylation Equivalents of Alcohols R. E. KEPNER and A. DINSMOOR WEBB Department of Chemistry a n d D e p a r t m e n t of V i t i c u h r e , University of California, Davis, Calif.
I
S T H E identification of the many small samples obtained by
fractional distillation of a grape brandy fusel oil i n this laboratory. a method for determining the weight of sample containing one equivalent of hydrosyl (the acetylation equivalent) on aliquots of 20 to 50 nig. was required. The method used ( 4 ) was a modification of the techtiiques of Smith and Bryant (3)and Baufmann ( 2 ) in which the pyridine was omitted and the alcohol. acetyl chloride, and toluene misture was reHused for 1 hour in a flask fitted with an irlterrla~ cold finger condenser, ~h~ flaslc \vas vented through a trap containing some standard sodium hydroxide solution in order t o prevent any losses of acid. This paper reports a further development of the method in which the reae-
tion flask is somewhat modified i n ortlri thxt smnllcr :iniount+ of alcohol snmple niay be analyzed kPP4RkTC S
The reaction Hask, as shown i n Figure 1. was ronstructed from a roun&bottomed flask of 100-Inl, capacity bJ- sealirlg oI1a standard-taper 24/40 joint. .I stopcock arld small funnel were sealed onto the Hask just below the ground-glass joint and an internal cold finger condenser was constructed by sealing a length of tubing 15 nim. in outside diameter to the smaller end of the male 21/10 joint. nletal clamp was desigrled ivhich permitted the condenser to be held firmly in the Bask. and the stopcock was held in p h c e by means of a spring-loaded retainer.
