cent. Below o 2 per cent. the increase in polarization due to the uranium-malic complex is so small that a small error in reading may make a relatively large error in the final result, while above 2 . j per cent. the increase in specific rotation tends to give high recoveries. The results shown in Table VI illustrate the applicability of the method t o natural products. The strawberry juice used as a solvent was highly colored and most of the readings had to be made in .;o or I O O mm. polariscope tubes. SUM M .4R Y.
( I ) When a neutralized solution of malic acid is treated with uranyl acetate, its rotation is increased approximately 2 8 O V. for each per cent. of malic acid in the solution; d-tartaric acid is the only other common acid which is affected in this way by uranyl acetate. Hence, in the absence of d-tartaric acid, malic acid may be determined quantitatively by treating its solution with uranyl acetate, polarizing, and multiplying the difference between this reading and that of the untreated solution by 0.036. The product equals the percentage of malic acid present. ( 2 ) In the presence of more than I O per cent. of reducing sugars and less than 0 . 2 5 per cent. of malic acid, the results may be affected by the action of uranyl acetate on the rotation of the sugar. Hence, in this case or when the amounts of sugar or malic acid are unknown, certain simple modifications are necessary. ( 3 ) For this determination, the most favorable limits of concentration of malic acid are between 0 . 2 to 2 . j per cent. The percentage error seldom amounts to more than j per cent. of the malic acid present. Twelve complete determinations may easily be made in four hours time, including two hours during which the solutions require no treatment other than frequent shaking. BUREAUO F CHEMISTRY.
~VASHINGTON, D C
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THE EFFECT OF PHOSPHORUS MANURING ON THE AMOUNT OF INORGANIC PHOSPHORUS IN FLAT TURNIP ROOTS.
s
By BURT L HARTRELL AND FREDERICK HAISMETT
Received June 21, 1911
It has been stated' that the percentage of total phosphorus in turnips is influenced b y the amount of available phosphorus in the soil. Advantage has been taken of this fact in ascertaining the relative deficiency of available phosphorus in soils. I t appears as a result of further study as if the inorganic phosphorus is influenced even more than the total ; if this is so its determination would prove more useful for this purpose than that of the total phosphorus. Microchemical examinations for inorganic phosphorus in sections of fresh turnips were made with a mixture o f , magnesium sulphate and ammonium chloride ;a only such an amount of ammonium hydroxide was used as was absolutely necessary, for fear that inorganic phosphorus would be developed from any phosphoproteins which might be present. Hartwell and Quantz. Jour B i d Chem , 7, XXXVIII (1910). Zimmermann, "Botanical Microtechnique ') 53 (1901)
Part of the material used for examination was from cooperative experiments with flat turnips, carried on in different parts of the State to secure data concerning the availability of the phosphorus in the soils. All of the plats which mill be considered in this connection were well supplied with lime, nitrogen and potassium. In each experiment, one plat did not receive any application of phosphate; a second received a liberal amount of acid phosphate; and a third received still more, in order to show whether the second had been supplied with enough to produce a maximum crop. As a result of the microchemical examination of small young turnips from five different localities, no crystals of ammonium magnesium phosphate were observed either in the turnips from the no-phosphate plats, or in those receiving the smaller application of phosphate, with the exception of a few crystals in the case of turnips from a single soil naturally well supplied with phosphorus. Where the larger applications of phosphorus were made, crystals were found, but small turnips as a rule appeared to contain only a small amount of inorganic phosphorus according to this test. Fresh turnips of a similar small size when examined later in the season, however, generally yielded a few crystals and those from the single soil referred to above contained considerably more than when previously examined. Early in the season the larger turnips from the nophosphate plats, on the contrary, yielded, generally, some crystals, although in case of certain of the soils, which were very deficient in phosphorus, scarcely any were found. Large turnips from the plats to which acid phosphate had been added invariably yielded crystals, and in some cases they were very abundant. As a result of a single season's observations, indications are afforded that the relative abundance of crystals formed by adding the magnesium-ammonium salt solution to sections of the larger turnips grown on different soils is correlated, to a certain extent a t least, with the relative amount of available phosphorus a t the disposal of the plant. Considerable quantitative chemical work mas done on turnips from two of the station plats in which the amount of available phosphorus was quite different as indicated b y the fact that the plat to which a liberal application of acid phosphate was made yielded thereby nearly twice as much as the other. The microchemical tests made on different dates revealed no crystals in turnips from the plat which was very deficient in phosphorus, even when the larger turnips were examined, except a few a t the end of the season; whereas the crystals were always plentiful in turnips from the phosphate plat. Although differences in the ratio of inorganic t o total phosphorus were found by precipitating the inorganic phosphorus b y magnesium, as well as b y the molybdenum, mixture, the results did not confirm the microchemical findings, in that considerable phosphorus was precipitated by these mixtures from turnips which yielded no crystals. It was feared, thereT
T H E J O U R N A L OF I N D U S T R I A L A N D EIVGIhTEERISG C H E M I S T R Y .
832
fore, that these . particular reagents precipitated a larger ambunt of inorganic phosphorus than existed originally, especially in case of turnips grown on the soil deficient in phosphorus. Their use was finally abandoned and the inorganic phosphorus determined in accordance with the following directions: grate portions of fresh turnips in the presence of sufficient acetic acid to equal about 2 per cent. of the moisture, finally squeeze the juice from the pulp, filter, add to an aliquot, barium chlorid solution with constant stirring, then carefully neutralize with ammonium hydroxid, allow to stand about a day, filter, wash, dissolve as much as possible of the contents of the filter in hot water and dilute nitric acid, wash, and determine the phosphorus in the filtrate, by molybdenum and magnesium mixtures in the usual way. In calculating the percentage of inorganic phosphorus in the turnips it was assumed that the percentage of phosphorus in the expressed juice was the same as t h a t in the moisture remaining with the pulp. A determination of moisture in the turnips, therefore, made it possible for the results t o be calculated on the basis of dry turnips. The above method was adopted after the following observations had been made regarding the amount of inorganic phosphorus, namely: that i t increased upon heating the natural juice; that it increased when the natural unheated juice was allowed to stand; that it did not increase on standing subsequently t o the addition of acetic acid; that it increased if an excess of ammonium hydroxid was added a t the time of precipitation with barium chlorid ; that it was fully recovered along with that in a standard solution of sodium phosphate added t o the juice; and that it was not increased by digesting the pulp with dilute hydrochloric acid, but that this digestion rendered its determination difficult on account of the presence of pectin-like compounds. The uncertainties as t o just what constitutes socalled inorganic phosphorus in work of this kind are fully recognized, and it is intended, as soon as material is available, t o subject the method to further tests regarding its accuracy. All things considered, however, it is not believed that the differences which are shown in the following table are exaggerated. DRY MATTER
P E R CENT. OF PHOSPHORUS PENTOXID CALCULATED TO THE OF TURNIP ROOTS
Ratio
of PZOSin Total in turnips
Total in juice, N o - P . plat pulp grated Inorganic, to that in in presence determined in P. plat, of acetic acid. the same juice. per cent.
.-
- ,
Oft. 17th, small turnips . 0.50 0.85 Nov. lst, small turnips ..... . 0 . 5 0 0.84 Nov. 1% large turnips. _ ., . . 0.44 0.84
.... .
0.22
0.61
0.02
0.13
58
15
0.23
0.53
0.03
0.24
60
13
0.31
0.52
0.06
0.26
52
24
I t may be seen b y reference t o the last two columns of the above table that although the content of total
h'ov.,
1911
phosphorus in turnips was nearly doubled by the addition of a liberal amount of acid phosphate, the content of inorganic phosphorus was increased about six-fold. , AGRICULTURAL EXPERIMENT STATION. RHODEISLANDSTATECOLLEGE, KINGSTON.
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TIN SALTS IN CANNED FOODS OF LOW ACID CONTENT, WITH SPECIAL REFERENCE TO CANNED SHRIMP. B y 11'.
D. BIGELOW AND R. F. BACON
Received September 28, 1911. INTRODUCTION.
It is customary to attribute the presence of tin salts in canned foods to the action of the acids of those foods upon the tin of the container. We usually think of the action of a food upon the tin as proportional to the acidity of the food. The acidity of many products ordinarily preserved in cans is so high and their effect on the tin lining of the container so marked as to offer a sufficient explanation of the amount of tin salts they contain, and until recently the high tin content of certain vegetables and other products of low acidity was overlooked or regarded as accidental. The interest lately awakened in the subject of tin salts has led to a more careful study of the question than has been given i t before and it is now recognized that several articles such as certain varieties of fish, beets, lima beens, asparagus, and pumpkin, though being almost without acidity, have a marked solvent action upon the tin lining of the container in which they are preserved. As far as we are aware, however, no explanation of this fact has been offered. TIK C O N T E N T O F CANNED GOODS VARYING IiX ACIDITY
AND AGE.
The relation of the acid t o the tin content of a series of canned goods, examined about six months after they were packed, is well shown b y the following table in which the acidity is expressed as acetic acid and the amount of tin is stated in milligrams per kilogram of the canned food and as milligrams of tin for each I O O mg. of acid. In the table those foods having the highest amount of tin in relation to their acidity are given first, and it is seen that the fruits whose action on tin is most familiar t o us because of their high acidity come last in the list with from I to less than 5 mg. of tin per I O O mg. of acid. I n some of the vegetables considered in this table the ratio of tin to acid is a little higher than in the case of some of the fruits shown. It is distinctly higher in all cases, however, especially if the pears, which are somewhat anomalous in one other respect, are exclqded. Moreover, in the fish and in a number of the vegetables the ratio of tin to acid is strikingly higher than in the fruit. In a general way the ratio of tin t o acid in the fruits appears t o depend on'the variety of the acid the fruit contains, the solvent action of citric acid, to which the acidity of raspberries and tomatoes is due, being less than that of malic acid. Pears appear to be an exception t o this rule, however, since, notwithstanding the fact t h a t
