I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
320
Application of the
Vol. 20, No. 3
u. s. P. Methanol Test'
Wm. L. 0. Whaley PROHIBITION
LABORATORY, u. s.
INTERNAL R S V E N U E SERVICE,
NEWORLEANS,
LA.
Observations of the result of applying the U.S. Pharmacopeia method2 for detection of methanol to distillates from Javoring extracts, perfumes, etc., collected f o r the purpose of determining the alcoholic strength of these substawes HE purpose of this paper is to point out the result of
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applying this test for methanol to some preparations in daily use, to show the effect of concentration of elcohol upon the sensitiveness of the reaction, and to point out the necessity of using caution in interpreting such tests when applied to material other than that upon which the method was worked out and commended. The method as given is to be applied to alcohol. If it is desired to use this test on other material, it must be modified to meet the new conditions. These observations are the outcome of experimental work to discover if certain flavors and so-called medicinal preparations, brought to our attention by the extremely favorable price quoted on the lots in question, were compounded from cleaned or purified denatured alcohols.
by some constituent of the preparation. Ginger ale concentrates have shown a similar development of a violet tinge upon being subjected to the test, Sensitiveness and Effect of Alcoholic Concentration
SO great a tendency to develop a coloration readily confused with the formaldehyde reaction in the methanol test was shown by such a large number of the samples investigated that the following procedure was carried out to get some limits for the methanol test: I n testing a sample of alcohol under normal conditions one will find 2 per cent methanol or find it absent. However, we suspected that in our samples every effort had been made to remove the methanol, if ever present, and accordingly it was desirable to know the smallest amounts that could be shown, as well as the intensity of the color under Application t o Fluid Extract of Ginger various concentrations. Two concentrations, listed in Table I as A and B, show To determine the alcoholic strength of fluid extract of ginger a 10-cc. sample was diluted to 100 C C . ~and approxi- the effect of the concentration of total alcohols as well as mately 100 cc. of distillate were collected and made exactly the amounts of methanol that may be detected. A was to the 100-cc. mark. Both the specific gravity and the re prepared by measuring 1 cc, of chemically pure methanol, fractive index were determined on a number of these distil- 4 cc. of refined absolute ethanol, and distilled water to make lates, and the alcoholic percentages corresponding to these 100 cc.; B was prepared from 1 cc. of methanol as in A , but two values looked up from suitable tables. There was usu- 49 cc. of ethanol and distilled water to make 100 cc. Thus, ally a wide discrepancy between these two values, and in while the content of methanol is the same in both cases, the consequence a number of these distillates have been sub- total alcohol concentration in B is just ten times that of A . A solution of 5 per cent ethanol was also prepared by measmitted to tests for methanol. 5 cc. of absolute alcohol and making up to 100 cc. with uring Several distillates from fluid extract of ginger, when tested for the presence of methanol, gave a faint bluish violet color- distilled water, to be used in making the final volumes to ation with the modified Schiff reagent. Three laboratories 5 cc. as called for in the test. tested the same sample. One reported methanol present, Solution A has 5 per cent total alcohols and 1per cent methanol. Solution B has 50 per cent total alcohols and 1 per cent and another reported methanol absent; so that the writer was in doubt as to whether this color was due to methanol methanol. The 5 per cent ethyl alcohol solution we will for convenience or to some other normal constituent of the ginger. call C. Ten cubic centimeters of the ginger were then diluted to Since the tests were made by taking the shown amounts 50 cc. with distilled water, made alkaline with 0.1 N caustic soda, treated with magnesium oxide and fuller's earth, and of C and using in parallel series with both A and B, we have liltered. The filtrate and precipitate were washed till there a series with not only steadily increasing amounts of methanol resulted a volume of 100 cc. filtrate and washings. Dis- but in the case of B a corresponding increase and also an increase in total alcohol concentration. tillate from this material gave a faint positive reaction. Some of the straight ginger extract was diluted to contain Table I-Sensitiveness of Methanol Test 5 per cent alcohol, and subjected to the test. A deep green SOLUSOLU- TIONS color appeared. Another portion was diluted with 50 per METHANOL INDICATION AND TIME REQUIRED TION A AND cent alcohol, saturated with sodium chloride, and extracted No. C B Solution A Solution B cc. cc. with ether. The ether extract gave no color reaction with 1 0 . 5 4 . 5 Neg. 30min. ? 2 hours the modified Schiff reagent after oxidation, but the salt 2 1.0 4 . 0 Neg. 30 min. Pos. 2 hours ) ? 30min Pos 2 hours Neg' 30 m i u s Neg' hours 3 1.5 3 . 5 water-alcohol portion gave a bluish green color on testing 4 2.0 3 . 0 Pos. 30 min: Pod. 2 hours for methanol in alcohol. 5 2.5 2 . 5 Pos. 15 min. Pos. 2 hours 6 None 6 . 0 Pos. 5 min. Pos. 4 days Comparison of the colorations just described with those under similar conditions using alcohol alone, alcohol with Since A only had 1per cent methanol in No. 1,the methanol methanol, and ginger extract with added methanol, led to concentration in the solution tested was only one-tenth of the conclusion that in this instance the color had been caused the original or 0.1 per cent; in No. 2, one-fifth the original 1 Received September 16, 1927. Published by permission of the head or 0.2 per cept, etc. We see that with the specified conof the Technical Division of the Bureau of Prohibition. centration of total alcohols one-half of 1 per cent will in a 9 U. S. Pharmacopeia X, p. 39. reasonable time give a positive reaction. With 1 per cent :Method of the Chemical Division of the Bureau of Prohibition, the color will hold for 4 days (possibly much longer). I n Washington, D. C.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
March, 1928
case of B , even in the sixth test, where there was 1 per cent methanol but 50 per cent total alcohols, no color had developed within 2 hours. A faint color did appear after about 4 hours, but it was gone the following morning. I n the B series the influence of increasing the amount of methanol was entirely offset by the increase in total alcohols. Modifications of the Test
I n order to test the smallest concentrations of methanol that could be detected, two modifications were made in the test as given in the U. S. Pharmacopeia. For convenience the methods have been designated as follows: No. 1,the original from the Pharmacopeia; No. 2, exactly the same except that the m a t e e l s were first distilled (25 cc. in 100) and distillates used; No. 3, 50 cc. of the solution diluted to about 200 cc., placed in a distilling apparatus, and oxidized at room temperature for 10 to 15 minutes with 5 cc. of 85 per cent phosphoric acid and 10 cc. of 3 per cent potassium permanganate solution. Should any pink color remain at the end of the time, it is discharged by sufficient 10 per cent oxalic acid solution, and then a flame applied and the distillate collected in a tube containing the modified Schiff reagent. Note-It was found necessary t o remove the oxidizing influence of t h e permanganate prior to heating; otherwise pure alcohol is so much attacked a s t o cause the similar color of acetaldehyde.
I n the test shown in Table I1 the 5 per cent ethanol previously described was used with sufficient of the other ingredient to bring the total concentration to the 5 per cent, in the amounts indicated. with Modified P r o c e d u r e OBSERVEDREACTIONFOR ADDED METHANOL AFTER 10 MINUTES INGREDIENT 5 % ETHANOL No. 1 No. 2 KO.3 T a b l e 11-Results
cc. ..
cc. ~.
5.0 Neg. Nothing 0.5 4.5 Pos. Methanol" 0.5 4.5 Pos. G 1y cero1 4.5 Neg. Acetaldehyde 0 . 5 4.0 ? b Acetaldehyde 1.0 0 . 5 g . 4 . 5 a n d 0 . 5 w a t e r Neg. Sucrose ? (faint) Invert sugar 0 . 5 g. 4 . 5 and 0 . 5 water Methanol" 0.5 4 . 5 of 50% alcohol Neg. 5 Methanol 5 cc. and distilled water to make total volume of 100 cc. b Fleeting; acetaldehyde when in sufficient concentration produces a purple color closely approximating in shsde t h a t of the formaldehyde compound. It appears under these conditions much more rapidly than does the formaldehyde color and is not permanent, always disappearing in from 5 t o 10 minutes.
I n the first and last sets we again find the same amount of methanol failing to be shown when the total alcohol strength has been increased. The preliminary distillation is therefore the procedure that in most cases must be used. This is undoubtedly true of practically all the substances under investigation in the next series of results. Color Tests
The phenomenon of giving a color reaction similar to that of methanol by distillates from fluid extract of ginger has already been noted. It was thought of interest to examine a larger number of preparations under conditions of the methanol test and to note the resulting color. The distillates obtained for the estimation of the alcoholic strength were used. They were distilled from the material made to dilutions according to the supposed alcoholic strength from the declared formulas, and after determination of the alcohol percentage they were diluted to correspond to the specified 5 per cent of the test. The resulting colors are described as closely as names could be selected for the colors and shades observed. (Table 111) No attempt was made to apply the tests on the raw material, consequently tests No. 2 and No. 3 are the only ones to report. '
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Discussion
The modification of the U. S. P. procedure of testing for methanol, mentioned in this article as method No. 3, waa undertaken in order to increase the sensitiveness of the test. However, it appears to give more interference from substances other than methanol than does the usual procedure. Thus oxidation and subsequent heating seem to cause decomposition in some instances, as in the case of sugars. Taggart4 has shown that in high concentrations of sugars under conditions encountered with sugarhouse products, temperatures above 115' C. alone are sufficient to produce formaldehyde from all these products. Table III- -Color T e s t s COLOR DEVELOP E13 IN 30 MINUTSS SUBSTANCE UNDER EXAMINATION No. 2 No. 3 Yellowish green Hair tonic Deep green Yellowish green Yellow 39D) Yellowish green Yellow Deep green Yellow Green (apple) Yellowish green Yellowish green Orange-yellow Yellowish green Yellow ComGound extract of vanilla Greenish yellow Yellow (lemon) Orange coloring Pale amethyst Yellow Yellow coloring Deep green Yellow Red colorin Antiseptic (Bcoataining oil of pepperYellow Green mint) Yellow Deep green Blackberry cordial Deep green Pale green Eau de cologne Orange-yellow Deep green Headache remedy Violet Violet Same with 1Y added methanol Intense purple Intense purple Same with added methanol Yellow Pale violet Same with 0 05 added methanol Eau de cologne g s a b o v e ) with 0.05% Greenish yellow Pale violet added methanol Greenish yellow Perfume, "extract" (from S. D. 40M) Greenish violet Pale green Green Hair dressing Greenish yellow Green Toilet water Greenish yellow Greenish violet ArtiBcial strawberry flavor Yellow Green Pure lemon extract Yellow Pink Orange flavor, imitation Yellowish green Yrllowish pink Essence of peppermint Yellow Yellow Grape compound Yellow Green Grape flavor base Pale violet Pale violet Imitation extract of pineapple Orange-yellow Greenish violet Aromatic extract of ginger Lemon-yellow Lemon-yellow Ethyl alcohol alone (control) a The sarsaparilla waq known t o contain oil of wintergreen. It was declared in the formiila and was also readily detected by the odor. However there was no reaction for methanol and the sample hnd been treated with' magnesium oxide and filtered prior to distillation, in order to remove oils, for the alcohol determination. Accordingly 50 cc. of the extract were diluted t o 150 cc., made decidedly alkaline with 0.1 N caustic soda solution, digested a t 100" C for 1 hour under a reflux condenser, then distilled and the first 50 cc. of the distillate separated into two portions. Onr of these was diluted and tested straight, the other was diluted, treated with fuller's earth. filtrred, and then tested. Both gave a violet color a t once.
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Methyl esters seem to be far less liable to cause complicatious than esters of the higher alcohols. It has been the experience of the writer that amyl esters very readily give oxidation products which are inclined to develop a violet color. The contributions of Georgia and Morales6 give the most advanced and complete information upon limitations of the method and interfering substances. The writer has found the reagent prepared from rosaniline salt to be more sensitive and more convenient than that prepared from fuchsin. The tests in this article were nevertheless made with the fuchsin reagent. Several additions might be made to the list of interfering substances6 given by Georgia and Morales. The writer has found that glycerophosphates and vanillin do not give the test. I n the procedure for alcohol determination used in our examples one must exercise care even in the interpretation of the results of Georgia and Morales. The conclusions of Haley,Bthough applicable under the specific conditions cited, are certainly not applicable to a large variety of materials which might be suspected of containing methanol. So prone are certain substances to produce shades suggesting traces of methanol, that a neglect of the precaution to prepare the sample of 5 per cent alcoholic strength caused I n d . Eng. Chcm., 2, 260 (1910). I b i d . , 18, 304 (1926). e Ibid., 18, 1312 (1926). 4
a sample of completely denatured No. 5 to get through the test with no indication of the 2 per cent of methanol which it contained. Conclusions
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Vol. 20, No. 3
INDUSTRIAL A N D ENGINEERING CHEMISTRY
322
When the procedure is strictly followed the findings are authentic for the materials for which the test was intended. By proper interpretations of the difficulties and suitable modifications, the test can be used on many other materials.
While under certain conditions confusing findings occur, these can usually be verified or eliminated by testing some of the same material to which a small quantity of methanol has been added. A method is suggested with a sensitiveness so high as to meet any requirements, but the advantages are offset by its ready response to the effect of interfering substances. The use of both methods on a sample will probably result in the detection of any methanol present, and if both give a positive indication methanol is very likely present.
Universal Tank Calibration Chart'
?
A. K. Doolittla T H E SEERWIN-~XLLIAMS Co., CHICAGO, ILL.
HE accompanying chart (Figure 2) was prepared to facilitate the work of inventorying the various liquid-
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storage tanks used by one of the large mankfacturers of nitrocellulose lacquers. After having calibrated a number of these tanks individually, laboriously integrating the volume in the end bulges by plotting the Cross sections on COordinate paper and counting the squares, the writer determined to prepare a chart that would be applicable to all cases.
Use of Chart By use of this chart it is possible to read, with an accuracy closer than 1per cent, the volume of liquid a t any depth in a cylindrical tank, whether horizontal or vertical, of diameter 2 to 10 feet and length 1 to 50 feet. The correction for the spherical end bulges on large tanks is also plotted on the same chart. To use the chart for horizontal tanks, start at the left margin with the depth (inches) of the liquid above the bottom of the tank. Move horizontally to the right till the curve corresponding to the diameter (feet) of the tank is reached. Then move vertically till the line corresponding to the length (feet) of the tank is reached, thence horizontally to the right margin where the volume in the cylindrical portion of the tank will be read in gallons. To determine the volume in the end bulges, use the curves on the top portion of the chart. Starting at the left with the depth in inches (same as above), move horizontally to the right till the diameter curve is reached, then vertically to read the volume (both ends) on the top scale. The endbulge correction is added to the volume in the cylindrical portion to give the total volume of liquid in the tank. To use the chart for vertical tanks, consider the depth of the liquid the length of the tank. Use the full diameter of the tank, disregarding entirely the values on the left margin. The volumes in tanks of diameters or lengths not in even feet can be readily interpolated from the chart. Preparation of the Chart
A = Jh2xdy;
A =
c
This function may be integrated from: 1
Received July 2,1927.
(h-r) d r z - ( h - r ) z
to
-r + rzsin-1 h- 3rrZ r TI
but the values are more readily plotted from the data in handbooks on segment areas. The second set of curves were plotted to: V = 7.4805 AL; L = constant where V = volume (gallons), A = area (square feet), and L = length (feet).
It will be noted from the above that the abscissas common to both sets of curves represent the area of the segmental cross section of the liquid.
Volume, gallon5
Figure 1
The construction of the curves for end bulge was more interesting from the mathematical point of view. I n standard tank practice the end bulge is designed to represent a segment of a sphere of radius equal to the diameter of the tank. As the integration of the volume considered as a segment of a sphere is too complex to admit ready calculation of the values, this volume was integrated as an ellipsoid of revolution.
The main portion of the chart was prepared by plotting on logarithmic paper two sets of curves to the same abscissa. The fist set of curves were plotted to: A = f ( h ) ; D = 2r = constant where A = area (square feet), h = depth (inches), and D = diameter (feet).
x = drs-(y-r)z
V = Lhrxydz
(1)
(both ends) where
X
= :drz-(z-r)z;
Q = r(2-
