V O L U M E 2 5 , NO. 5, M A Y 1 9 5 3 complexation constants for these elements ale enormous, no large excess of unreacted chelating agent ia required for the reaction to go to completion. The excess reagent probably functions here b y displacing absorbed complexes into solution, thus achieving the excellent Qepnrationobserved. EFFECT OF TIY AYD ZIRCO\IURI
I n separate qtudies the effect of tin and zirconium on this qeparation n as investigated. The results of those experiments are considered important because these elements are commonly a'sociated with the earth oxide minerals, although usually in small amountq. K h e n added to the solution prior to the hydiolysis step, neither of these elemerits interfered x i t h the letention of the iron and manganese b j the chelating agents. Moreover, the tin apparenty a a - retained quantitatively in the filtrate I n any separation that might be planned, it would thus go n i t h the iron and manganeqe and not appear in the titanium distillate. Zirconium, on the other hand, divided in thi. operation. The amount going with the iron and manganese vai ied considerably, but ucually was betTveen 60 and 907,. I n concentrates where ziiconia is a major component, this separation cannot be used without further investigation. On the other hand, the zirconia is often a very minor constituent, and its determination is then not too important. It is easily recovered from the filtrate by making
a25 the solution aliout 6 JI n i t h sulfuric acid and then precipitating it with phosphoric acid. ACK3-OK LEDG3f E S T
The authors ~ o u l dlike to acknon-ledge the help of Russell H. Atkinson for some direct experimental assistance in the course of this investigation and the advice of Joseph Steigman and Sorman Adler on several important points. LITERATURE CITED
(1) dtkinson, R. H., Steigmati, J., and Hiskey, C. F., ;1s.i~. CHEX. 24, 480, 484 (1952). (2) Biederman, IT,, and Scha-arzenbach, G., H e b . Chim. Acta, 3 1 , 4 5 9 11948). (3) Britzinger, H., Thile, H., and JIuller, U., 2. anorg. allgem. Chenr., 251, 285 (1943). (4) Hiskey, C. F., Sewman, L., and .Itkinson, R. H., ANAL.C H m r . , 24, 1988 (1952). ( 5 ) Jones, S. S.. and Long. F. .I., J . Phvs. Chem.. 56, 25 (1952). (6) Palilla, Frank C.. 11,s.thesis, Polytechnic Institute of Brooklyn, Iiovember 195 1. (7) Schoeller, TT. R., "Analytical Chemistry of Tantalum and Xiobiurn," London, Chapman and Hali, Ltd., 1937. RECEIVED for review Septemher 9 , 1952. Accepted January 27, 1953. Experimentai d a t a taken from thesis submitted b y A. L. Batik t o the chemistry faculty of the Polytechnic Institute of Brooklyn as part of the requirements for the 31,s.degree in chemistry. June 1 9 j 2 .
Thermometer Calibration for Determination of Capillary Melting Points STANLEY C. BUXCE Rensselaer Polytechnic Institute, Troy, 4'.1.. HEmiomwERs
used in the determination of capillary melting
Tpoints may be calibrated n i t h a series of pure substances of
hnonn melting points. Lists of compounds suggested for use as standards for calibration which are found in Iahoratory textbooks are, however, generally unsatisfactorv. I n most cases the compounds chosen are poor standards because they are difficult to purify or store, or because the melting points of the pure compounds are not accurately knonn. I n the work reported here, a survey a a s made to find compounds TThich are suitable standards. I n order to test their suitability as standards, a number of these compounds v ere purified by recrystallization, their purity TTas confirmed by cooling curve measurements, and they were employed in calibrating thermometers under the conditions for use in melting point determinations.
Calibrations may be extended to higher temperatures by the use of reference melting points with pure metals. PURIFICATIOY OF REFERENCE CORIPOUh-DS
Six compounds were chosen from the list in Table I, and saniplea were purified, as indicated in Table 11. I n each case, the purification procedures were readilL- accomplished; crj-stallizations were conducted, in general, so as to obtain maximum purity a t the expense of efficient recover>- of material.
Table I. Compounds L-seful for Melting Point Standards Compound
Melting Point,
C.
COMPOUNDS FOR B'IELTIR-G POIhT STAYDARDS (21, 48.1
A list of compounds Those melting points are suitable standurds for thermometer calibration is presented in Table I. These vere chosen to meet, as closely as possible, t n o criteria. They may be purified without excessive labor or access to special apparatus, and the melting points of the pure compounds determined by a t least tx-o investigators check to within 0.2" C. Only compounds for which a t least one of the measurements has been made by thermocouple or resistance thermometer are included. The list could probably be extended to include more compounds in the lower melting point range, but the number of compounds n hose melting points have been accurately measured by several investigators is surprisingly limited. Burriel-3Iarti undertook to prepare a list of compounds suitable for calibration of Anschutz thermometers and found it necessary to determine melting points for each of his purified compounds (3). His n-ork, which appears to have been not sufficiently recognized, has formed the basis fora part of the present list; the original work and the summary of data on pure compounds by Timmermans ( 2 5 ) have also been useful. It would be desirable to have confirming data on the melting points of the highest melting compounds listed in Table I.
(fa
(21)
Benzoic acid Urea hlannitol Succinic acid p-Kitrobenzoic acid Anthraquinone
132.8 (IO)
The purit,y of each of the final samples was checked by determining its cooling curve (8. 2 2 ) . The apparatus used need not be refined, and the thermometer need not be calibrated in order t o determine that a sample has a constant freezing point during the first third of the solidification time. I n all cases, the temperature during t,he initial portion of the plateau as found to vary less than 0.2" C. indicating that the compounds n-ere sufficiently pure that their initial freezing points n-ere within 0.2" C. of the true freezing point. Since measurements of capillary melting points can be made reproducible only within this limit unless great care is used, this vas considered satisfactory.
826
ANALYTICAL CHEMISTRY ACKNOWLEDGAMENT
Table 11. Purification of Reference Compounds Compound p-Dichlorobenzene
Source Eastman Kodak
Triphenylmethane
Benzene and chloroform
co.
Urea
l l e r c k and Co.
Succinic acid
Eastman Kodak co.
pl-Sitrohenzoic acid
Oxidation of p-nitrotoluene
Anthraquinone
Eastman Kodak
co.
o-Benzoylbenzoic acid
Purification Recrystallized from ethyl alcohol and Nont-.k, and ethyl alcohol Dried a t 10 mm. over calcium chloride Recrystallized from acetic acid and Sorit-A, and ethyl alcohol Dried a t 10 mm. a t 50’ C. Recrystallized from water and Sorit-A, and methyl alcohol Dried a t 10 mm. a t 70’ C. Recrystallized from water and Xorit-A, and water Dried a t l l O o C. Decolorized with Sorit-A in 10% solution in sodium hydroxide precipitated by sulfuric acid, ?e: crystallized from acetic acid Dried a t l l O o C. Recrystallized from nitrohenzene and Xorit-A, toluene, and benzene Dried a t 110’ C . Sublimed a t 10 mm., recrystallized from toluene and Sorit-.l Dried a t 110’ C.
The suggestions and criticism of G. J. Janz and the assistance of a number of students in the experimental work have been helpful. LITERATURE CITED
Andrew-s, D. H., Lynn, G., and Johnston, J., J . .4m. Chenz. Soc., 48, 1274 (1926).
Block, H., 2.physik. Chem., 78, 385 (1912). Burriel-Marti, F., Bull. S O C . chim. Belg., 39, 590 (1930). Campbell, A. N., and Prodan, L. .1.,J . Am. Chem. Soc., 70, 553 (1948).
Chernois, N. D., and Entrikin, J. B., ”Semimicro Qualitative Organic .Inalysis,” pp. 21-34, S e w Tork, Thomas Y. Crowell Co., 1947. Deffet, L., Bull. SOC. chim. Belg., 44, 41 (1935). Desvergnes, L., M o n . sci., 15, 149 (1923). Francis, F., and Collins, F. J. E., J . Chem. Soc., 1936, 137. Hershberg, E. B., IND.EXG.CHEW,A a a ~ED., . 8, 312 (1936). Hrynakowski, K., and Smocskiewicsowa, A , , Roczniki Chem., 17, 167 (1937).
Johnston, J., and Jones, E. P., J . Phus. Chem., 32, 593 (1928). AIcSeight, S. A , , and Smyth, C. P., J . Am. C h e m . SOC.,58, 1718 (1936).
XIorris, R. E., and Cook, W..1.,Ihid., 57,2403 (1935). Morton, .1.A , “Laboratory Technique in Organic Chemistry,” pp. 21-32, Sew Tork, lIcGraw-HiIl Book Co.. Inc., 1938. Parks, G. S.,and Anderson, C. T., J . .4m. C h e m . Soc., 48, 1508
USE IY THERMOMETER C4LIBRATIO1
Pure compounds n i t h known melting points, such as these, may be employed in standardizing thermometers for accurate capillary melting point determinations. A single thermometer, partially immersed in one of the refined types of electricallv heated and stirred baths (9) may be calibrated a t a number of points under the same conditions as n-ill obtain in actual melting point determinations ( 5 ) . This method, for which these standards are particularly suited, is an alternate to the use of a series of calibrated short-range thermometers used under conditions of total immersion. Its accuracy is limited by the reproducibility of the melting point determination, which may be within 0.1’ C. in careful work (8,14), and by the purity and the accuracy of the knoivn melting points of the standards. It has been demonstrated, by checks with pure compounds, that melting points determined x i t h thermometers calibrated with these purified standards are in error by no more than 0.2’ C.
11926).
Pearce, J. S . ,and Snow, R. D., J . Phys. Chem., 31,231 (1927). Pollatschek, H., Z. phflsik. Chem., 142, 259 (1929). (18) Schwab, F. W., and Wichers, E., J . Research S u t l . Bur. Standards, 32, 253 (1944). Ihid., 34, 333 (1945). Shnidman, L., and Sunier, .I.d., J . P h y s . C h m . , 36, 1232 (1932). Skau, E. L., J . Am. Chem. Soc., 52, 945 (1930). Skau, E. L., and Wakeham, H., “Determination of Melting and Freezing Temperatures,” in Weissberger, .I., “Physical Methods of Organic Chemistry,” pp, 49-105, 2nd ed., Part 1. Sew York, Interscience Publishers, Inc., 1919. (23) Smith, R. H., and Andrews, D. H., J . Am. C ~ F V SOC., L . 53, 3644 (19) (20) (21) (22)
(1 93 1). (24) Speyers, C. L., Ibid., 18, 146, (1896). ( 2 5 ) Timmermans, J., “Physico-Chemical Constants of Pure Organic Compounds,” New York, Elsevier Publishing Co., Inc., 1950. (26) Viseur, G., Bull. SOC. chim. Belg., 35, 426 (19263.
RECEIVED for review September 2 , 1952. Accepted February 7 , 1952.
A Specific Color Reaction for Sugars HENRY TAUBER Venereal Disease Experimental Laboratory, U . S . Public Health Sercice, School of Public Health, University of .Vorth Carolina, Chapel Hill, N. C . ( I ) that under certain conditions ketoI hexosesbeenor reported compounds Tvhich contain ketohexose units give T HAS
rise to a reddish-purple color in the presence of aminoguanidine and sulfuric acid, Aldohexoses in quantities equivalent to the ketohexoses did not produce a color, but larger quantities gave a color identical n-ith that given by the ketoheuoses. The addition of a small quantitv of dichromate to the sulfuric acid produces, in the presence of aminoguanidine, an intense blue color Tvith aldohexoses or carbohydrates TI hich contain only aldohexose units (glucose, galactose, glucose-1-phosphate, mannose, trehalose, lactose, maltose, melibiose, glycogen, starch, dextrin, cellulose; \\-hatman, ashless pov der), and a wine-red color 11 ith ketohexoses or carbohydrates containing ketohexose units (fructose, sorbose, sucrose, melezitose, raffinose, inulin). Pentoses (arabinose, xylose, ribose) give a yellow color under similar conditions. The colored compounds which form in this reaction are very stable. REAGENTS
Aminoguanidine Solution, T v o and five-tenths grams of aminoguanidine sulfate monohydrate are dissolved in 100 ml. of distilled water. This reagent is stable a t room temperature.
Dichromate-Sulfuric Acid. One milliliter of a 1% potasrium dichromate solution is dissolved in 100 ml. of concentrated sulfuric acid. This reagent is usable for 1 month. COLOR REACTION FOR SUGARS
Four tenths of a milliliter of a 0.2% sugar or polysaccharide solution is placed in a test tube. This concentration is essential because of color variations a t different carbohydrate concentrations. Four tenths of a milliliter of aminoguanidine solution is added with mixing. Then 1 ml. of dichromate-sulfuric acid is added. Immediately after mixing, ketohexoses and carbohydrates which contain ketohexose units give rise to a wine-red color. Aldohexoses or carbohydrates which contain aldohexose units only, give rise to a deep blue color within 1 minute. Pentoses produce a yellow color within 1 minute. The control is colorless. This is probably the easiest procedure for distinguishing betn-een sugars. LITERATURE CITED
(1) Tauber, Henry, J . B i d . Chem., 182, 605 (1950). R E C E I E D for review December 31, 1932. Accepted January 31, 1’353.
