ANALYTICAL
1166 The pure precipitate could not be recovered quantitatively because i t tended to be peptized by washing with water or dilute sodium hydroxide. Such peptization can be prevented considerably by washing with 1%magnesium sulfate solution which adjusted to pH 10 with sodium hydroxide. ACKNOWLEDGMENT
The author thanks Philip DiMeola for his aid with the turbidity measurements.
CH‘EM~STRY
LITERATURE CITED
Cheng, K.L., ANAL.HEM., 26,1038-40 (1954). (2) Cheng, K. L., and Bray, R. H.,Ibzd.. 25,655-9 (1953). (3) Piibil, R., DoleZal, J., and Sirnon, V., CoUection Czechoslov. (1)
Chem. Communs., 18,780-2 (1953). (4) Sidgwick, N. V., “Chemical Elements and Their Compounds ” Vol. I. D. 118. Oxford Universitv Press. N e w York 1950. (5) Thorne, p. C. L., and Roberts, ‘E. R., “Ephraim’s Inorganic Chemistry,” 5th ed., p. 457, Interscience, Sew York, 1949.
RECEIVED for review December 15, 19.54. Accepted February 17, 1955
Ceriometric Determination of Sugars A. A. FORIST and 1. C. SPECK, JR. Kedzie Chemical Laboratory, M i c h i g a n State College, East Lansing, M i c h .
T w o procedures have been developed for determination of small changes in sugar concentration by ceric per.chlorate oxidation. Both methods are applicable to estimation of semimicro quantities of sugars. Results obtained for several reducing sugars are given.
being the number of carbon atoms in the sugar molecule. Among the sugars tested only DL-glyceraldehyde was incompletely ovidized in 1 hour. I n Table 11, a &hour oxidation period waa required to achieve the theoretical consumption of oxidant for this substance.
T
HE oxidinietrio determination of glycerol, glucose, sucrose, and related compounds by means of the ceric perchlorate re.agent was described by Smith and Duke ( 1 , 2 ) . Two modificartions of the procedure have been useful in investigating the kinetics of certain reactions involving small changes in the con$centrations of various sugars. Results obtained M ith t n o pentoses and one triose are given, which evtend the list of tcarbohydrate substances determined by oxidation n ith this reagent.
Table I.
Ceriometric Determination of Sugars
Sugar
Added, RIg.
~ I E T H OID 30.03
D-Glucose
D-Xylose
30.03
D-Ribose
36.03
~~-Giyceraldehyde
36.03
REAGETVTS
Ceric perchlorate, approximately 0.28.V in 4 M perchloric acid. One liter of G. F. Smith Chemieal Co. reagent-grade ceric perEhlorate acid (in 6 M perchloric acid) is mixed with 172 ml. of 12% perchloric acid. The resuiting mixture is diluted to 2 liters with distilled water. This reagent is standardized against sodium oxalate or sodium arsenite and is stored in the absence of ‘light. Ceric perchlorate, 0.01 t o 0.03~V,in 25f perchloric acid. This solution is prepared by appropriate dilution of the above reagent. It is standardized daily against sodium oxalate or sodium arsenite and is also stored in the absence of light. Sodium o d a t e , 0.1800Ar, in 0.1M perchloric acid. Sodium arsenite, 0.1300N. Aecurately weighed arsenious oxide (approximately 13 0 grams) is dissolved in a mixture of 10 grams of anhydrous sodium carbonate and 1 liter of u-atci. T h i s solution is then diluted to 2 liters with water. Osmic acid, 0.01M, in 0.1M sulfuric acid. Yitro-ferroin indicator, 0.02511.
METHODI1 18.02
D-Glucose a
Found, RZg. 36.08 36.21 36.94 36.13 36.16 35,85 35.91 36.02 35.82 36.13 36.10 35.97 36.06 35.91a 35.85= 18.09 18.12
1s
Results for 4-hour oxidation.
06
The present procedures offer the advantages of sensitivity to small changes in sugar Concentrations and titration to the disappearance of the indicator color rather than through a serim of color changes as occurs in the reverse titration. These methods may be readilv altered to accommodate different ranges of sugar concentration by appropriate changes in reagent concentrations.
PROCEDURES
Method I. T o 18 to 36 mg. of the sugar, in aqueous solution ,not esceeding5ml:in volume, add 20 nil. of the 0.28:\- ceric perchlorate reagent. A4110wthe oxidation to proceed a t 26” C. for 1 ‘hour, then add 2 5 ml. of the sodium oxalate solution to the mixture. ‘Titrate the excess oxalate ion with the 0 . 0 3 5 ceric perchlorate reagent to a nitro-ferroin end point. Method 11. To 15 to 21 mg. of the sugar, in aqueous solution not exceeding 5 ml. in volume, add 10 ml. of the 0.28N ceric perchlorate reagent. After allowing the oxidation to proceed a t , 2 j 0 C. for 1 hour, add 2 drops of the osmic acid solution followed by 15.00 nil. of the arsenite solution to the oxidation mixture. Then titrat,e the excess arsenite u-ith the 0.01S ceric perchlorate reagent to a nitro-ferroin end point.
Table 11. Effect of Time on Ceric Perchlorate Oxidation of DL-Glyceraldehyde Time,
Hr.
1 2
DISCUSSIOli
Theory 6.0
3.75
LITERATURE CITED
(1)
Typical results are given in Table I. All calculations are based #onconsumption of 2n equivalents of cerate per mole of aldose, n
Equivalents of Cerate Consumed per Mole of Sugar
Smith, G. F., and Duke, F. R.. IND. ENG.CHEM.,;IK.LL. ED., 13, 558 (1941).
(2) Ibid.. 15, 120 (1943). RECEIVED for review October Z:, 1954.
Accepted .January 7, 1935.
