90 2
T H E J O U R N A L O F I N D U S T R I A L A N D EA’GIiVEERING C H E M I S T R Y
tion and excessive washing and even after prolonged washing t h e results were usually high. Cobalt free from nickel gave good results when oxidized with bromine water, b u t even here the washing required was excessive and t h e method is much inferior t o the one given above using sodium perborate. I n conclusion Tve would state t h a t cobalt may be determined in the presence of nickel by oxidation in alkaline solution 11-ith sodium perborate, removing t h e excess of t h e perborate b y boiling, and after the addition of potassium iodide and dilute sulfuric acid, titrating with a standard sodium thiosulfate solution. CHCXICAI. LABORATORY, UNIVERSITY OF DENVBR DESVER,COLORADO
T H E COMPOSITION OF SOUND AND FROZEN LEMONS WITH SPECIAL REFERENCE T O T H E EFFECT OF SLOW THAWING ON FROZEN LEMONS By H. S. BAILEYA N D C. P. TILSON
Received Mag 29, 1916
IKTRODUCTORY
T h e work described below was undertaken as a result of th,e freeze of January 6 > 1913,which destroyed a portion of the citrus crop of Southern California and was especially severe on lemons. While no temperature charts were made a t San Dimas, t h e district from which the material was collected, Mr. Woods, foreman of t h e San Dimas lemon house, says: “On t h e 6th of January, the d a y preceding the freeze, there was a very high wind and the temperature went below t h e freezing point early in t h e evening. -2 l o v temperature was maintained until 6.30 next morning, when i t began t o move up.” T h a t t h e injury t o lemons, which almost always follows a heavy freeze, is due t o a rapid thawing of the frozen fruit, rather t h a n t o t h e low temperature t o which they have been subjected, seems t o be t h e general opinion of citrus growers. This assumption is apparently substantiated by t h e fact t h a t in groves where a night of frost is followed b y a warm, bright, day, t h e damage is greater t h a n in orchards which have suffered an equally low temperature during t h e night b u t warmed u p more slowly t h e following day. I n other words, when a cloudy morning or a heavy smudge blanket keeps t h e groves cool until toward noon, t h e fruit is less injured b y a freezing night t h a n if t h e sun comes out hot early in the day. This is in harmony with the well-known fact t h a t living animal tissues suffer greater injury from freezing if the thawing out be rapid t h a n when it takes place gradually. I n t h e hope of obtaining further d a t a upon t h e effect of gradual thawing upon frosted citrus fruit, Mr. Horsford, Manager of t h e San Dimas Lemon Association, had a quantity of t h e fruit which was frozen on t h e night of January 6 , 1913, picked, beginning a t 7 o’cloclc t h e following morning and continuing nearly all t h a t day. This was stored as fast a s gathered in t h e packing house a t a temperature of 45 t o j o o F., where it would thaw slowly. At t h e time t h e freeze occurred there was already in storage in his house a quantity of sound lemons picked two days previously a n d several boxes of these were set
Vol. 8, S o .
TO
aside for comparison later with frozen fruit. To supply t h e third set of samples, t h a t of frozen fruit thawed rapidly, several trees were left unpicked in t h e orchard, from which were gathered t h e frosted lemons for storage. An opportunity was thus afforded t o make a comparative study of fruit picked before t h e frost, and therefore, normal; fruit picked and stored immediately after the frost; and frozen fruit remaining on t h e trees. All this fruit came from t h e same grove of Eureka lemons. D E S C R I P T I O X O F SARIPLES A N A L Y Z E D
One packing box of fruit picked January 4, two days before t h e freeze, and one box picked January 7 , the d a y after the freeze, v e r e selected and placed side b y side in storage a t a temperature of 45 t o j o o P. Beginning January 1 6 , a sample of a dozen or more lemons was taken a t random from each box and another dozen picked fresh from the grove. These were wrapped in t h e regular tissue paper wrappers, packed in a vc-ooden box, and sent b y express t o t h e Citrus By-products Laboratory in Los Angeles, and analyzed as soon as possible after being received. Similar series of samples were taken a t intervals of about a meek until the first of M a y following. JIETHODS
O B ANALYSIS
PRuIT--’CVhen received, t h e lemons were weighed on a torsion balance and immediately p u t in a battery jar filled with water and covered with a ground glass plate t o remove all surplus water. T h e fruit was then taken out and t h e jar refilled with water, the amount thus required being equal t o the volume of t h e fruit. From the weight of the fruit and volume of mater it displaced, the specific gravity was calculated . A P P E A R A K C E O F FRcIT-The lemons were cut in halves 71-ith a sharp knife and t h e condition of t h e cell structure noted. Perfect lemons, showing no evidence of having been frosted, are designated as “Sound,” those in which about 2 0 per cent of t h e cells appeared desiccated, t h a t is, dried and shriveled, due to having been injured b y t h e frost or t h e resulting thawing of t h e frozen tissues, “Slightly frozen.” The remainder, where t h e cut surface showed more t h a n 20 per cent of t h e cells affected, were considered badly frozen and so denoted. P E R C E K T A G E O F jurcE-After this examination t h e half lemons were wrapped in a heavy canvas press cloth, 2 4 in. square, and squeezed in a hydraulic press with about r j o o lbs. pressure. The juice and pulp were collected and weighed separately and t h e percentage of each obtained. Owing t o t h e fact t h a t a n appreciable amount of juice was absorbed and retained b y t h e press cloth, the more exact figure for t h e quantity actually present in the fruit was obtained b y deducting t h e weight of t h e pulp from t h a t of t h e original lemons. This figure, divided b y t h e weight of fruit pressed, gives the calculated percentage of juice and is the value so tabulated. These figures were used in calculating the percentage of citric acid in the fruit, which probably makes these latter values a little higher t h a n would be obtained had t h e samples been larger. SPECIFIC
GRAVITY
OF
Oct., 1916
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
S P E C I F I C G R A V I T Y O F JuIcE-The Specific gravity of t h e juice was determined at 2 0 ' C. b y means of a spindle. ACIDITY O F JUICE-Immediately after taking t h e specific gravity I O cc. of t h e juice were pipetted from t h e cylinder a n d titrated against N / z sodium hydroxide solution, phenolphthalein being used as a n indicator. F r o m t h e specific gravity a n d t h e acid equivalent t h u s obtained, t h e percentage of acid as citric, plus one molecule of water, was calculated. SOLIDS IN JUICE-solids were determined in t h e juice b y drying I O cc. in lead dishes for 8 hrs. in a n air b a t h a t a b o u t 9; t o 100' C. Owing t o t h e difficulty in controlling t h e oven a n d t h e action of t h e acid on t h e metal dishes, t h e solids determinations are probably only approximations. ANALYTICAL RESULTS
The results are given in t h e accompanying tables a n d show t h e effect of t h e frost on t h e stored a n d unstored fruit. It is t r u e t h a t t h e sound lemons were in storage two days earlier t h a n t h e frozen ones, b u t this would have very little, if a n y , effect upon t h e relative condition of t h e two lots a t t h e time t h e first analysis
was made, ~j days after t h e freeze. Owing t o t h e small samples used for analysis, peculiarities in individual lemons h a d a n undue influence upon t h e
903
figures obtained for t h e entire sample. Too much importance must not be given t o t h e individual determination. As has already been intimated this work was undertaken without previous preparation, on t h e spur of t h e moment, when t h e material became available. I t is perfectly obvious t h a t instead of t h e small samples of a dozen lemons, a t least a n entire box should h a v e been used for each analysis, b u t under t h e circumstances samples of this size were out of t h e question. TABLE11-COMPARISONS OF SPECIFICGRAVITIES,
JUICES
AKD
ACID CONTENTS P E R CENT C I T R I C D a t e SPECIFIC GRAVITIES JUICE YIELD Per cent I n Juice In AnalOF FRUIT SU FS FT SU FS FT SU ysis SU FS FT 0.933 0.914 0.837 49.6 42.4 41.1 6 . 5 6 . 9 5 . 1 3 . 2 1/21 0.913 0.886 0.789 37.4 39.5 31.9 7 . 2 6 . 6 5 . 3 2 . 7 1/25 0 , 9 2 0 0.886 0.779 42.1 35.9 26.5 7 . 1 7 . 3 5 . 3 3 . 0 2/ 3 0.940 0.923 0.710 44.8 3 4 . 3 28.7 6 . 8 6 . 9 4 . 5 3 . 0 0.952 0.920 0.729 41.4 3 3 . 9 2 5 . 3 7 . 0 6 . 8 4 . 7 2 . 9 31: 0.951 0.904 0.701 46.2 45.5 2 9 . 8 7 . 3 7 . 2 4.8 3 . 4 2/15 0.944 0.870 0.724 4 2 . 8 3 5 . 2 28.4 7.2 6 . 6 4 . 1 3 . 0 2/25 0.931 0.898 0.773 40.1 3 5 . 6 31.6 7.4 6 . 8 4 . 9 3 . 0 2/27 0.926 0.882 0.730 4 1 . 4 3 6 . 9 26.3 7.3 7 . 6 4 . 8 3 . 0 3/ 4 0.967 0.894 0.714 42.7 3 2 . 4 2 6 . 3 7 . 3 7 . 2 3 . 7 3 . 1 3/ 7 0.913 0.870 0.713 40.2 36.7 3 3 . 3 7 . 4 7 . 1 4 . 1 3 . 0 3/11 0.949 0.879 0.682 40.7 3 5 . 3 3 0 . 0 7 . 4 7 . 3 3 . 7 3 . 0 3/14 0.954 0.920 0.713 3 9 . 7 3 7 . 3 26.1 8 . 2 7 . 8 4.7 3 . 3 0.934 0.840 0.753 44.1 3 3 . 9 3 4 . 8 8 . 3 7 . 3 4 . 1 3 . 7 $11; 0.968 0.918 0.766 4 8 . 3 3 9 . 4 3 5 . 0 7 . 6 7 . 6 4 . 1 3 . 7 4/25 0.991 0.889 0.722 3 3 . 3 3 6 . 5 31.6 8 . 1 7 . 4 4 . 3 2 . 7 5/ 2
CITRIC ACID Fruit
FS FT 2.9 2.6 2.6 2.4 2.3 3.3 2.3 2.4 2.8 2.3 2.6 2.6 2.9 2.5 3.0 2.7
2.1 1.7 1.4 1.3 1.2 1.4 1.2 1.5 1.3 1.0 1.4 1.1 1.2 1.4 1.4 1.4
Disregarding t h e n t h e great irregularities in t h e individual figures, it is evident t h a t t h e frozen fruit stored immediately after freezing is much more like t h e unfrozen fruit t h a n like t h e frozen fruit left on t h e trees. T h e specific gravity of t h e fruit and t h e percentage of acid i n t h e juice are nearly t h e same for the two lots in storage, while these values for frozen fruit left on t h e trees are considerably lower. T h e percentage of juice in t h e frozen fruit in storage is about a mean between t h a t of t h e unfrozen fruit in storage a n d t h e frozen fruit on t h e trees. T h e figures show t h a t t h e frozen fruit which remained in the orchard is n o t nearly so rich in citric acid as t h e sound fruit or as t h a t frozen b u t immediately placed in cold storage. This fact is of special importance t o those interested in t h e manufacture of citrus byproducts, a n d is fully confirmed b y t h e work, on a much larger scale, of t h e By-products Laboratory in t h e manufacture of citric acid from t h e frozen fruit of t h e 1913 crop. T h e amount of citric acid in t h e juice of one ton of frozen lemons, taking t h e figures from twelve runs of fruit between January 18, 1913, t o M a y 19, 1913, varied from 14.03 lbs. t o 30.14 lbs., with a n average of 20.16 lbs. Corresponding figures on four runs of sound lemons from April 18, 1914,t o June 8, 1914,were 42.75, 49.44, 46.56 lbs. citric acid in juice of one t o n of lemons. I n this connection, however, i t should be mentioned t h a t there is apparently no decrease i n t h e oil content of lemons due t o freezing, a n d t h a t t o n for t o n t h e more frozen a n d consequently lighter t h e fruit t h e greater t h e yield of oil. It has been pointed o u t t h a t the frozen fruit remaining on t h e trees decreased in specific gravity a n d its juice in percentage of solids a n d acidity. T h u s t h e increasing lightness in t h e orchard fruit is evidently due both t o t h e decrease in t h e amount of juice actually present a n d t h e percentage of total solids in t h e juice.
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T H E JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
There is b u t little change in the specific gravity of t h e fruit held in storage during the first 60 t o 7 0 days, and even u p t o t h e end of t h e experiment t h e increase is slight a n d may be accounted for b y a normal drying-out or withering of t h e fruit. But with t h e fruit t h a t remained on t h e tree there is a t first a very marked decrease in specific gravity and t h e n apparently a gradual increase. It was noticed in cutting this orchard fruit t h a t during t h e latter half of t h e observation period t h e lemons appeared t o be filling out a little. S UJ?hf A R Y
I n so far as a preliminary experiment of this kind can be considered as giving definite results, t h e following conclusions may be drawn: I-The lemons t h a t remained on t h e trees after being frozen retained less juice and considerably less acid t h a n t h e fruit picked immediately after being frozen and stored a t a temperature of 45 t o 50' F. 11-The frozen fruit left on t h e trees decreased rapidly in specific gravity due t o t h e loss of juice a n d acid and t h e formation of thick, puffy skins, dried-up cells and hollow centers. 111-Lemons picked immediately after being frozen and stored under ordinary packing house conditions retained somewhat less juice t h a n the unfrozen fruit, b u t t h e composition of t h e juice was nearly the same, and in weight and appearance t h e slowly thawed lemons compared well with normal fruit. We wish t o acknowledge our indebtedness t o Mr. G. 'A7. Hosford of t h e San Dimas Lemon Association for his valuable suggestions and hearty cooperation, and t o t h e association for so generously supplying us with t h e fruit used in this investigation. BUREAUO F
CHEMISTRY, WASHINGTON
AN IMPROVED METHOD FOR THE DETECTION O F ARACHIDIC ACID By ROBERT H. KERR
Vol. 8, No.
IO
METHOD
Weigh out 20 g. of t h e oil t o be tested in a 300 cc. Erlenmeyer flask, pour in 2 0 0 cc. of 95 per cent ethyl alcohol, and heat t o boiling on t h e steam bath. When t h e alcohol is boiling add I O cc. of t h e potassium hydroxide solution. Saponification begins immediately and is soon complete. After t h e saponification has been completed add a few drops of phenolphthalein and neutralize t h e excess alkali with t h e alcoholic solution of acetic acid. Next add jo cc. of t h e 5 per cent magnesium acetate solution and heat t h e whole mixture t o boiling. Allow t o cool t o room temperature with occasional shaking and then place in a refrigerator a t a temperature of I O t o I j o C. and leave until next day. Filter off t h e solution, wash t h e precipitate twice with j o per cent alcohol a n d three times with distilled water, and return t o t h e flask in which precipitation took place. Pour I O O cc. of hot distilled mater into the flask and add sufficient dilute sulfuric acid t o decompose the magnesium salts. Heat until t h e separated acids form a clear layer. Cool t h e flask, pour off t h e acid solution, add I O O cc. of hot water. When the f a t t y acids have melted and solidified, pour off water as before. Free t h e cake of acids of water as far as possible b y draining; dissolve in I O O cc. of 90 per cent alcohol and separate t h e arachidic acid by crystallization, according t o t h e present provisional method of the Association of Official Agricultural Chemists as given in Bulletin 107, Revised, Bureau of Chemistry, p. 146. The method as outlined above has been used on a number of samples of peanut oil and mixtures of peanut and other vegetable oils. T h e results obtained are qualitative only, no attempt having been made t o apply t h e method for quantitative purposes. It has been found t o be capable of detecting j per cent of peanut oil in olive oil, cottonseed oil, soy bean oil and corn oil. These results are quite as good as t h e best which have ever been obtained with Renard's method. RCREAU O F ANIMAL ISDUSTRY,
WASHINGTON
Received May 16, 1916
T h e method described below for t h e detection of arachidic acid in peanut oil and mixtures of oils containing peanut oil has been found t o offer certain advantages over t h e Renard method adopted b y t h e Association of Official Agricultural Chemists. These advantages consist in greater convenience, lessening of t h e number of operations, reducing t h e amount of attention required, and avoidance of t h e use of ether. REAGENTS
Potassium Hydroxide Solutioiz-Dissolve I O O g. of stick potassium hydroxide in I O O cc. of water. Magnesium Acetate Solution-Dissolve I O g. of magnesium acetate in a mixture of I O O cc. distilled water and I O O cc. of 95 per cent alcohol. Acetic Acid Solution-Mix 50 cc. glacial acetic acid with 150 cc. of 95 per cent ethyl alcohol. jo cc. concentrated Suljuric Acid Solution-Mix sulfuric acid with 150 cc. of distilled water. 90 per cent E t h y l Alcohol (by volume).
THE HYDROLYSIS OF ETHYL-SULFURIC ACID AND THE ASSAY OF AROMATIC SULFURIC ACID, U. S. P. By W. B. D. P E N X I M A N ,W.W. RAKDALL, c.0. M I L L E R Received September 1, 1916
AND
1,. H. ENSLOW
Aromatic sulfuric acid is a mixture of sulfuric acid, ethyl-sulfuric acid, certain aromatics and alcohol. I t is prepared b y bringing together, according t o t h e U. S. Pharmacopoeia, 111 cc. of concentrated sulfuric acid and 7 0 0 cc. alcohol, and, after t h e mixture has cooled, adding jo cc. of tincture of ginger, I cc. of oil of cinnamon, and sufficient alcohol t o bring t h e total volume up t o one liter. The proportion of ethyl-sulfuric acid present depends upon the strength of t h e sulfuric acid and alcohol used and upon the length of time t h e mixture remains hot, and probably increases t h e longer the liquid stands, even when cold. The Pharmacopoeia (Eighth Revision) is not concerned with t h e ethyl-sulfuric acid: its only demand is t h a t t h e mixture shall contain not less t h a n 2 0
