INDUSTRIAL AND ENGINEERING CHEMISTRY
March. 1931
335
Some Organic Acids in Honey'" E. K. Nelson and H. H. Mottern DIVISIONOF FOODRESEARCH, BURBAVOF CHEMISTRY AND SOILS,WASHINGTON, D . C.
The volatile and non-volatile acids in fifteen samples the honeys. An 80 per of honey have been determined. The total volatile cent solution was prepared honey have been menacids range from 0.011 to 0.051 per cent, and consist from 4 kg. of sucrose, and 5 tioncd in the literature mainly of a mixture of formic and acetic acids. Sage g r a m s each of malic and ( 3 , 4 , 6 , 8 )but , little has been honey has the largest amount of acetic acid (0.046 c i t r i c a c i d were a d d e d . published as to the nature per cent), and tulip honey has the largest amount of The s o l u t i o n was diluted and a m o u n t of the nonformic acid (0.024 per cent). Citric acid accompanied with water and alcohol and volatile acids. Heiduschka by malic acid was found in all samples. Succinic precipitated with lead sub(7) reports the presence of acid was identified in the samples of higher acidity acetate exactly as in the case lactic, malic, tartaric, oxalic, (sourwood, cotton, and t u b-).. of the honev samnles. The and succinic acids in honey total acids ricoverid from the but the m e t h o d s he used, since they depended on separations and oxidation reactions lead precipihte had an acidity equivalent to 82 per cent of the original acidity. An aliquot of 100 grams of the solution, that were not specific, were not above criticism. It is well known to honey producers that different floral representing one-fiftieth of the total quantity and containing varieties of honey have marked differences in quality and 0.1 gram each of citric and malic acid, was analyzed. The flavor. I n order to ascertain the possible relationship of the amount of malic acid recovered was 0.079 gram and of citric organic acids to these flavor differences, as well as to furnish acid, 0.079 gram. Therefore, it is safe t o assume that the further information on the organic acids present in American figures for citric and malic acids represent not more than honeys, fifteen samples of honey of different floral varieties, 75 per cent of the amounts actually present. There was a large titratable acidity in all samples which produced in 1929, were examined. These honeys were collected from various parts of the United States, with one a m - was not accounted for by the sum of the acids determined. ple from Hawaii,a and were representative of the chief com- This discrepancy is partly due to incomplete separation of mercial varieties on the American market. There was no the lead salts from such a dilute solution of the organic acids, but other acids of unstable character, related to the sugars, evidence of fermentation in any of these samples. may also be present, which were not identified. Determination of Non-Volatile Acids Determination of Volatile Acids It was the intention to apply the ester distillation method to the separation and identification of the non-volatile acids The volatile acids were determined by steam-distilling in honey but, owing to the very small amount of acids present 100 grams of honey diluted to a volume of 150 cc., keeping and the large quantity of honey required to yield a sufficient this volume constant, and collecting 1 liter of distillate. The amount of the mixed esters for a fractional distillation, this combined volatile acids were obtdned by adding an amount was not found to be feasible except in the case of tulip honey. of sulfuric acid equivalent to the alkalinity of the ash and For the separation of the non-volatile acids from each distilling a second liter of distillate. other, an unpublished method was used which was devised The distillates were titrated with 0.1 N sodium hydroxide by Hartmann and Hillig, of the Food, Drug, and Insecticide and evaporated to small volume. The organic acids were Administration. However, this method does not distinguish liberated with an exact equivalent of sulfuric acid, and the between malic and succinic acids, so that the results given solutions were boiled with mercuric oxide for 20 minutee for malic acid include any succinic acid that may be present. under a reflux condenser in order to destroy the formic Citric acid was weighed as pentabromoacetone (5), checked acid. for identity by its melting point. The solutions, after cooling, were filtered from exce8s Malic acid was precipitated as the calcium salt, which was mercuric oxide, acidified with sulfuric acid, and the acids ignited and the residual calcium oxide titrated with 0.1 N other than formic were distilled and titrated. hydrochloric acid. I n a few cases, where the amount of The acids sometimes had a faint odor sugge8ting the presmaterial was sufficient, the malic acid determination was ence of higher volatile acids, but in every case, when esterichecked by the tentative method of the A. 0. A. C (1). fied with ethyl alcohol, the ethyl acetate odor was recognizThe non-volatile acids were precipitated from the diluted able. honeys by lead subacetate. To 5 kg. of honey, diluted with The total quantities of formic and acetic acid found were 3 liters of water and 6 liters of alcohol, sufficient lead acetate corrected for the amounts remaining undistilled according to was added to insure complete precipitation. The precipi- Dyer (2). tate was allowed to settle overnight, the supernatant liquor Separation of Succinic Acid wa.9 siphoned off, and the precipitate was washed with 50 per cent alcohol. Succinic acid was separated from some of the honeys by The completeness of the precipitation of the acids as lead extracting the honey (diluted with water and acidified with salta from the very dilute alcoholic sugar solutions was tested hydrochloric acid) with ether in a continuous-extraction by running a check analysis with known amounts of malic and outfit. The partly crystalline residue from the ether was citric acids corresponding to the average total acidity of purified by crystallization from water and identified as suc1 Received December 12, 1930. Presented before the Division of cinic acid by optical crystallographic data4 and by the melting Agricultural and Food Chemistry a t the 80th Meeting of the American point. Tests for tartaric acid gave negative results in all
HE v o l a t i l e acids in
T
Chemical Society, Cincinnati, Ohio, September 8 t o 12, 1930. 9 Food Research Division Contribution 85. a The selection of samples was made with the assistance and advice of the Bee Culture Laboratory of the Bureau of Entomology.
CaSeS. 4 Obtained by G. L. Keenan, of the Food, Drug, and Insectidde Administration.
INDUSTRIAL AND ENGINEERING CHEMISTRY
336
Results Malic and citric acids were found in all samples examined. Formic acid, formerly assumed to be a n important acid in honey, is present in a relatively small amount, confirming the observations of Fincke (4), Heiduschka (6), Farnsteiner (s), and others. The results obtained are given in Tables I and 11. Examination of Tulip Honey I n the examination of tulip honey, 4 kg. were diluted with water and alcohol and precipitated with 100 grams of lead subacetate. The precipitate was filtered and washed. Carbon dioxide was passed through a water suspension of the precipitate, and it was then filtered and washed again, The acids recovered from this precipitate were extracted with ether, yielding a crystalline acid which, after recrystallization, was identified by the melting point and optical crystallographic data as succinic acid. The residual acids were converted into ethyl esters, yielding 6 grams of the mixed esters. This mixture, fractionated a t 10 mm., afforded 0.2 gram boiling a t 80-125" C., 0.33 gram boiling a t 125-140" C., 0.7 gram boiling a t 140-160" C., 0.52 gram boiling at 160-170° C., and 2.4 grams boiling a t 170" C. Levulinic acid was identified in the lowest fraction by means of its hydrazide. This undoubtedly resulted from the action of the alcoholic hydrochloric acid during esterification on sugars occluded by the lead precipitate. Malic acid was found in the second, third, and fourth fractions by means of its hydrazide, melting at 178-179" C., while the fifth and largest fraction yielded citric hydrazide, melting at 103-105" C. and further identified by optical crystallographic data. A separate extraction with ether of 200 grams of the honey, acidified with hydrochloric acid, yielded 0.024 gram of purified succinic acid, equivalent to 0.012 per cent. The predominating non-volatile acid of tulip honey, therefore, is citric acid (about 0.04 per cent). It also has about 0.012 per cent of succinic acid, and a smaller amount of malic acid.
~'01.23, SO.
Table I-Volatile Acids of H o n e y FORMIC ACETIC FORMICCOM- ACETIC Cox- FORMIC ACETIC SOURCE FREE BINED FREE BINED TOTALTOTAL
VARIETY
%
%
%
%
Tulip Md. 0.007 0.017 0,009 Mesquite Calif. 0.003 0.004 0.002 Sage Calif. 0.004 0.001 0.039 Orange Calif. 0.004 0.002 0.003 Sourwood Va. 0.007 0.004 0.002 Spanish needle Ill. 0.010 0.012 0.005 Alfalfa Utah Nil 0.001 0.007 Clover Ohio 0.004 0.002 0.002 Star thistle Calif. 0.004 0.003 0.003 Cotton Tex. 0.006 0.005 0.006 Sweet clover Colo. 0,002 0.006 0.003 Fireweed Wash. 0.006 0.003 0.007 Alfalfa Calif. 0.007 0.003 0.004 White clover" Ohio 0,007 0.005 0.002 Algarroha Hawaii 0.002 0.009 0.004 This honey has a green color. The producer honey or other honey may be mixed with it.
Y
o
%
.-
0.007 0.024 0.016 0.003 0.007 0.005 0.007 0.005 0.046 0,002 0.006 0.005 0.008 0.011 0.010 0.004 0.022 0,009 0.005 0.001 0.012 0.004 0.006 0.006 0.002 0.007 0.005 0.006 0.010 0.012 0.003 0.008 0.006 0.006 0.009 0.013 0.003 0.010 0.007 0.005 0.012 0.007 0.010 0.011 0.014 states that sweet clover
Acids of H o n e y ALKALINFREE ITY OF MALIC CITRICS ~ C C I N I C VARIETY SOURCE ASH ACIDITY ASH ACID ACID ACID 70 Cc./lOO nramsa % % Sourwood Va. 0.28 23.0 -30.0 0.003 0,006 Present Spanish needle Ill. 0.18 17.3 22.0 Trace 0,001 Alfalfa Wash. 0.06 13.5 6.3 Trace 0,001 Trace (?) Clover Ohio 0.05 13.0 5.3 Trace 0.001 Star thistle Calif. 0.09 23.0 7.5 Trace Trace Cotton Tex. 0.34 22.5 42.0 0.056 0.008 Present Sweet clover Colo. 0.04 10.0 4.3 Trace 0,001 Fireweed Wash. 0.07 9.5 8.0 Trace 0,001 Alfalfa Calif. 0.17 27.5 20.5 0.002 0.002 White clover Ohio 0.11 19.5 13.5 Trace 0.001 Algarroba Hawaii 0.52 13.5 37.0 Trace 0.001 Mesquite Calif. 0.15 14.0 20.0 0.011 0.007 Orange Calif. 0.06 14.0 7.5 Trace 0.001 Calif. Sage 0.06 11.5 6.5 Trace 0,001 a Expresse d in terms of 0.10 ' .V solutions. Table 11-Non-Volatile
Literature Cited (1) Assocn. Official Agr. Chem., 1925, p. 213. (2) Dyer, J . B i d . Chem., 28, 452 (1917); Table V. (3) Farnsteiner, 2. Nahr. Genussm.,113, 598 (1908). (4) Fincke, I b i d . , 23, 255 (1912). (5) Hartmann and Hillig, J. A m . Assocn. OBicial Agr. Chem., 13, 99 (1930). (6) Heiduschka, 2. Nahr. Genussm., 21, 375 (1911). (7) Heiduschka, Pharm. Zentralhalle, 62, 1051 (1911); Schzueiz. Wochschr., 49, 725 (1911). (8) Utz, Pharm. Post, 4 1 (6-7), 69 (1908).
Increasing the Purity of Common Salt' Thos. B. Brighton a n d Carl M. Dice DEPARTMENT OB
- ? I N I N G AND
hfETALLVRGlCAL RESEARCH,UNIVERSITY
F THE approximately 7.5 million tons of salt produced
0
each year in the United States, about 30 per cent is obtained from the evaporation of brines, either natural or artificial. Solar evaporation makes up only a small portion of this and is confined to the more arid parts of the country, especially to the vicinity of the Great Salt Lake in Utah and to parts of California. The brines from the Great Salt Lake contain as a rule somewhat over 20 per cent of solids, and of this approximately three-quarters is sodium chloride. The other constituents might empirically be said to be chiefly sodium sulfate, magnesium chloride, and potassium chloride. This natural, nearly saturated brine, available in unlimited quantities, makes an excellent raw material for the production of high grades of salt. Manufacture of Salt from Great Salt Lake Brine The water from the lake is first pumped to settling ponds, each covering about 250 acres. Here it is allowed to remain 1
Received December 15, 1930.
3
OF
UTAH.
AND
u.
s
BUREAUO F MINES,SALT LAKE CITY, UTAH
until, owing to solar evaporation, it is practically completely saturated. The brine then flows by gravity to smaller crystallizing ponds, each 10 acres in area. Flow through these ponds is continuous throughout the evaporating season and is so regulated that only sodium chloride crystallizes from the solution. Other salts are not present to the saturation point in the outflowing bitterns and so are removed. Care must be used, however, in the autumn as the nights become cool, to see that the ponds are drained before sodium sulfate crystals form. At this time of year the brines are near saturation with Glauber's salt even a t daytime temperatures. Hence the salt harvest begins usually in early September. I n the bottom of each crystallizing pond is a floor of salt 12 to 15 inches thick. This is maintained and kept clean by the rapid and complete evaporation of a small amount of brine a t the beginning of the evaporation season. On top of this floor the salt crystals form during the summer to the depth of 3 to 5 inches. At the end of the evaporating season the bitterns are drawn off and the salt is allowed to drain. The salt layer is broken up by tractor-driven plows down
