April 15, 1931
INDUSTRIAL AND ENGINEERING CHEMISTRY
The value of the ore was 81.69 per cent according to the Bureau of Standards. Several samples of the ore were treated with hydrochloric acid, etc., without removing the residue, filtered hot, the iodide added a t once. and the whole titrated. The results were 0.2 to 0.7 per cent high. If the solutions are standardized under the same conditions as the titration, the are almost as accurate as those given above. However, for
135
a quick method where greater accuracy is not required, this should be satisfactory. Literature Cited (1) Treadwell and Hall, “Analytical Chemistry,” VOI. 11, 7th ed., p. 6-54, Wiley, 1928. (2) Willard and Coke, J . Am. Chem. sot., 43, 2208 (1920). (3) Willard and Kassner, I b i d . , 62, 2402 (1930). This work was completed before their paper was published.
Measurement of Color in Solutions of White Sugars’,’ J. A. Ambler and S. Byall BUREAUOF CHEMISTRY AND SOILS, WASHINGTON, D. C.
HE grading of w h i t e
The measurement of the colors of white sugars was equally serviceable. A soluplaced on a reproducible, accurate basis by matching tion of the sugar to be graded sugars by the color of their solutions has the colors of water solutions of the sugar against a was prepared by dissolving been d o n e in the past by standard caramel solution made by diluting Balch’s 120 g a m s in water, making up to 200 cc., adding 15 to 20 No. 5 maple sirup color standard solution. For the means of more or less arbitrary methods which lack any determination of color of hard candies made from grams of Filter-Cel, and, after exact meaning in terms of the the sugars, the candies were dissolved in water and the t h o r o u g h mixing, filtering colors of the solutions matched against a diluted No. through paper on a Buchner absolute quantity of coloring matter p r e s e n t . For soh9 maple sirup color standard solution. The color of funnel. Theclearfiltratewas the barley candy is not related to the color of the placed in the other side of the tions of white sugars, grading original white sugar. colorimeter and the color deby means of Stammer degrees termined by finding the volis not satisfactory because of the extreme paleness of the colors encountered. I n grading ume of the standard solution necessary to match exactly the the sugars produced during a campaign, or in comparing the color of 100 cc. of the fdtered sugar, solution. Uniform light colors of sugars of different yearly campaigns, some reproduci- source was assured by making the readings in a dark room and ble standard is necessary if reliable comparisons are desired. using a daylight lamp to illuminate the solutions. This method This is now possible by use of standards adapted from the of reading gives a direct measure of the amount of coloring color standards for maple sirup as defined by Balch (2),who matter present; the deeper the color, the greater the number has worked out exact specifications for obtaining reproducible obtained. If a sugar solution is darker than the standard, caramel solutions of given depth of color. These standard the color of 50 cc. (or, if necessary, of 25 cc.) of the finknown specifications are based on the amount of light transmitted may be matched against the standard, and the reading obby the caramel solution at 560 mho tained is then to be multiplied by 2 (or by 4) to make the Since the color of most white sugars is caused by occluded determination comparable with the rest of the series. For measuring the color of the barley candies it seemed , and adhering films of the colored liquor from which the sugar crystallized, it is in most cases very similar to that of caramel, aesirable, though it is no€ absolutely necessary, to use a especially in the paler shades generally encountered. I n only stronger standard and a more dilute solution of the candy bea comparatively few cases does the color assume a grayish cause of the deeper color of the candies. Accordingly a No. 9 or greenish hue. When such abnormally colored sugars are Balch maple sirup color standard solution was diluted exactly found it is impossible to grade them with the normal-colored as before (10 grams to 100 cc.) and measured against a ones by any method short of complete spectroanalysis. I n filtered solution of 30 grams of the candy made up to 200 cc. many cases the grayness of a sugar is caused by particles of with water. The use here of a stronger standard and a weaker dust or of carbon which have not been eliminated by filtration candy solution obviates the necessity of using more than or which may have accidentally become admixed with the 100 cc. of the standard solution. This method is flexible and susceptible of various modificasugar during the final stages of drying and sacking. If these particles are removed from the solutions it will often be found tions as the exigencies of the work require. For example, by that a gray sugar will yield a normal-colored sirup. using the same standard, it is possible to estimate the inThe method here described was used satisfactorily during crease of color occurring during storage of sugar, or during the past year in grading samples of white sugar collected boiling or concentration of sirups or liquors. The color may from various factories, and also in grading the color of the be expressed on the basis of total dry solids, total sugars, hard barley candies made from them by the standard hard total non-sugars, or any other desired basis. For the grading of white sugars, direct readings are sufficient, since the figures candy test (1). The standard color solution for the sugar so~utionswas obtained by calculating to a total solids or a total sugar basis made from Balch’s No. 5 maple sirup color standard solution are directly proportional to the readings found, because the by taking 10 grams and diluting it with water to 100 cc. This quantity of impurities present in the white sugar is proporwas placed in one side of a colorimeter, in this case one of tionately smaller than that of the experimental error. If desired, the readings may by Proper *calculationsbe conthe Campbell-Hurley type, although other types would be verted to percentage transmittancy or to extinction co1 Received October 30, 1930. Presented before the Division of Sugar efficient, since Balch’s standards are based on the percentage Chemistry at the 80th Meeting of the American Chemical Society, Cintransmittancy, from which the extinction coefficients may cinnati, Ohio, September 8 to 12, 1930. * Contribution No. 99, Carbohydrate Division, Bureau of Chemistry readily be derived. and Soils. A few of the results obtained are shown in Table I.
T
ANALYTICAL EDITION
136 Table I SUGAR a
b
2 a
COLOR
COLOROA CANDY^
%
%
85 55 50 45 78 42 100
41 50 42 40 120 39
85
VOl. 3; No. 2 I
SUGAR
i h j
k
1
m
n
coLoR
COLOROF CANDYa
%
%
200 166 198 60 92 71 86
47 60 24 25 83 36
it is evident that the color of the sugar has no definite relation to the color of the candy produced from the sugar, and consequently there is no need of using the same standard color solutions in grading the sugar and the candy. The only comparisons that may be drawn are those between the sugars themselves and those between the candies themselves. Literature Cited
Stronger standard and more dilute solution used.
From these values of the color in the sugar and in the candy
(1) Ambler, Manufacluring Confectionery, 1, No. 1, 17 (1927). (2) Balch, IND. ENG. CHEM., 22, 255 (1930).
Impurities in White Sugars I-Determination of Phosphorus’sz S. Byall and J. A. Ambler BUREAUOF CHEMISTRY AND SOILS,WASHINGTON, D. C.
The importance of traces of impurities in sugar is T IS common knowledge very often possible to debeing recognized more and more, necessitating the among sugar c h e m i s t s termine the total quantity of development of methods of analysis of greater sensiand technologists that in a group of compounds havtivity. Inorganic and organic phosphorus compounds evaluating white sugars for ing in common some characwhich are present in the plant find their way into the certain uses the o r d j n a r y teristic r e a c t i o n or atomic juices and eventually into the white sugars crystallized gravimetric, volumetric, and grouping. The n i n h y d r i n from these juices. The Briggs modification of the physical chemical methods test for a m i n o acid comBell-Doisey coerulo-molybdate method of determining of analysis are i n a d e q u a t e . pounds (1) is a group test phosphates is sufficiently delicate to show the amounts For example, two samples of this character, since it is of inorganic phosphorus and, by difference, will show of white sugar may be pracspecific for no i n d i v i d u a l the amounts of organic phosphorus present in sugar. tically i n di s t i ngu i s h a b 1e amino acid, polypeptide, or The test is capable of showing as little as 0.3 p . p . m . when examined for ash, inother hydrolytic product of Pz06 when applied to a 10-gram sample. Analyses vert sugar, sucrose, pH, color, albumin, but is given by the of a large number of white sugars of all kinds have turbidity, and so forth, and class of compounds which revealed the fact that organic phosphorus compounds yet one sample may show a contain an amino group in are not entirely eliminated by modern methods of greater t e n d e n c y t o w a r d the alpha position to a carsugar production. caramelization on heating or boxyl group. With the remay be more susceptible to f i n e m e n t of a n a l v t i c a l fermentation than the other. Such differences in behavior methods and technic it may eventually be possible t’o submust be caused by impurities which are present in quantities divide such groups of related compounds into smaller ones, so minute that either they have b‘een formerly considered un-’ or in some cases to determine chemical individuals. important and therefore not determined, or they are capable Phosphorus Compounds in White Sugars of estimation only by special methods of a sensitivity greater than that of the methods in general use. It has long been known that phosphates are present in the In studying the causes of such differences in behavior, juices of the sugar cane and of the sugar beet. I n the procthe first point of attack is from the analytical end. Only esses of manufacture of sugar, the lime which is added in the when the amounts of the impurities are known is it possible, clarification of the juice combines with the phosphates present by adding appropriate quantities of each to pure sucrose, to to form the relatively insoluble calcium phosphates But determine from any desired viewpoint the effect of each foreign because the latter are appreciably soluble, a small quantity substance and of combinations of them. The determination of inorganic phosphates always remains in the liquors and, of the quantities of contaminants which are present only as will be shown, m6ay often be determined in the white sugar. in traces is often difficult, not only because of the lack of Organic phosphorus compounds such as lecithin and the methods of sufficient sensitivity but also because of the nucleic acids also occur in the tissues of the sugar cane (6) extreme reactivity of sucrose itself toward chemical reagents. and of the sugar beet (4). They will therefore pass into Therefore, it is necessary to devise methods or to modify the mill and diffusion juices and will be subjected to the existing methods so as to increase their sensitivity and over- action of lime in the clarification. The lecithins on treatcome interference by the sugar. Several such methods ment with alkalies yield among their hydrolytic products have been worked out and will be the subjects of the first glycerophosphoric acid which, on account of the solubility part of a series of publications on the “Impurities in White of its calcium salt (6), will be removed from the liquors only Sugars.” The effects of these impurities will be discussed to the extent that it is adsorbed by the compounds precipilater in the series. tated in the sludge. The nucleic acids are more-stable toAlthough in dealing with traces of organic substances ward lime than the lecithins and probably are hydrolyzed to a it is rarely possible in the present state of knowledge even to less extent during the processes of sugar making. Neither detect the presence of an individual organic compound, it is type of these phosphorus compounds responds to the ordinary tests for phosphates until the organic portion of their mole1 Received November 28, 1930. cules has been destroyed or removed by hydrolysis. The 2 Contribution No. 105, Carbohydrate Division, Bureau of Chemistry occun-ence of organic phosphorus in white sugars has not and Soils.
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