NOTES ON ANALYTICAL PROCEDURES Isopropyl Alcohol i n C o t t o n JAMES
H. KETTERING,
H E Conrad technique ( 2 ) for determining max in cotton fiber was found more efficient and complete, within a reasonable extraction period, than any other technique tried. This method, long used a t the Southern Regional Research Laboratory employs ethyl alcohol as the extracting solvent. The substitution of isopropyl alcohol as the extracting solvent is the subject of the present report. Isopropyl alcohol, n hich has many of the properties of,ethyl alcohol, is plentiful, readily available, cheaper than even denatured ethyl alcohol ( I ) , and free from federal tax and accompanying restrictions. Moreover, it yields identical results when substituted for ethyl alcohol in the Conrad technique. Proof that this substitution can be made without sacrificing accuracy should, therefore, increase the usefulness of this excellent analytical procedure.
I n the application of the Conrad technique in the following experiments, the alcohols used throughout were the purified azeotropic water-alcohol mixtures, 9570 ethyl alcohol distilled from potassium hydroxide, and 91 yGisopropyl alcohol decanted from sodium hydroxide and then dlstilled. To facilitate the phase separations, 100 nil. of water were used instcad of the 75 ml. recommended in the original Conrad procedure. Wax determinations were made on a series of cotton bagging materials using 95YGethyl alcohol and then repeated, substituting 91% isopropyl alcohol as the extracting medium. The procedures were identical in all other respects. The results (Table I) show that isopropyl alcohol extracted practically the same percentages of the waxy substances as the ethyl alcohol, the small differences observed being within the usual limits of experimental error. Experiments in which the quantities of alcoholic extract from identical cotton fabrics were given as a function of time (Table 11) showed that no difference existed between ethyl and isopropyl alcohols in extraction time. Isopropyl alcohol extracts ~
Series
I.
Table 111. Sugars Transferred to Chloroform b y Ethyl and Isopropyl Alcohol b y Distribution from Solutions Containing 1 Gram of Sugar Sugar Taken Sucrose Dextrose Levulose Blank determination
MQ.
0.0
0.8 0.8 0.0 0.0 2.4
0.1 0.0 0.0 0.0 0.1
1.6
0.3 0.0
0.0 0.0
CONCLUSIONS
The substitution of isopropyl for ethyl alcohol as the extracting solvent in the Conrad method for the determination of wax in cotton fiber does not alter the values obtained. Extraction with isopropyl alcohol is accomplished as rapidly and completely as with ethyl alcohol, with no apparent damage to the resulting fabrics, The general characteristics of the extracts obtained with both solvents appear to be identical; and both solvents eliminate the transfer of sugars to the isolated wax.
% 0.71 0.74
0.64 0.54 0.33
Table
Ethyl Alcohol
Mo.
Conrad ( 2 ) has pointed out that no appreciable quantities of the sugars occurring in cotton fibers, such as perhaps sucrose, dextrose, or levulose, are transferred from ethyl alcohol to the chloroform with the wax. To compare the relative quantities of sugars transferred to chloroform by ethyl alcohol and by isopropyl alcohol, duplicate 1-gram samples of each sugar were dissolved in 100-ml. quantities of isopropyl alcohol and in like quantities of ethyl alcohol in the separatory funnels, chloroform and water were added, and the determination was completed in the same way as for wax. Table I11 shows that isopropyl alcohol, probably because it is a better solvent for sugars than ethyl alcohol, carried all the sugars into the watery layer, allowing none to be transferred t o the chloroform. I n this respect, isopropyl alcohol seemed superior to ethyl alcohol as a solvent in wax determinations. The differences, however, are not significant. So'ap, when present, is determined as wax by the Conrad technique. This characteristic is not changed by substitution of isopropyl for ethyl alcohol.
Wax Values E t h y l alcohol Isopropyl alcohol solvent solvent
%
448
Isopropyl Alcohol
Wax Values b y Conrad M e t h o d
Treatments
NO.
La.
as rapidly as ethyl alcohol and, when the same techniques are used, yields the same quantities of wax. Moreover, the general appearance of the two extracts was identical, and no differences were detected in the properties of the extracted fabrics.
EXPERIMENTAL
Table
Determination
Southern Regional Research Laboratory, N e w Orleans,
T
~~
Wax
antichlor Kiered. soured, chlorine bleach, sour
0.40
0.40
0.41
0.41
II. Speed of Extraction of Wax from Cotton b y Isopropyl and Ethyl Alcohol
ACKNOWLEDGMENT
Wax Values Extraction Time Hoys
Isopropyl alcohol
Ethyl alcohol
%
%
0.83
0.79 0.87
0.81 0.85 0.87 0.86
Appreciation is expressed to Carl M. Conrad for helpful criticisms and advice on the work here presented. LITERATURE CITED
0.84 8.85 0.85
'
(1) Anon., Oil Paint Drug Reptr., 148 (No.l l ) ,9-10 (1945). (2) Conrad, C.M., IND.ENG.CHEM.,ANAL.ED.,16,745-8 (1944).
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