Table ll.
Mixture
Analyses of Monosaccharide Mixtures
Amount Com- present, ponents mg.
Recovery, % (av. of two)
1
Glucose Galactose Mannose
102 99.5 101
2
Glucose Galactose Mannose Rhamnose
3 3
97.5 101 101 98.5
Glucose Galactose Mannose Ribose
2 2 2 2
101 99.25
4
Glucose Galactose Mannose Fucose
2 2 2 2
100.5 100 101 99.8
5
Glucose Galactose Mannose Arabinose
4 4 4 4
99 99.5 106 94
3
101
101
standard (Table 11). Recovery on duplicate analyses is within f 1% for all the sugar mixtures except mixture 5 in which one of the anomers of arabinose overlaps the a-D-mannose peak. Low values are thus obtained for arabinose and are accompanied by correspondingly high values for mannose. Sugar mixtures that are separable on this column can therefore be readily quantitated with a high degree of accuracy despite the anomerization of each sugar into two to four TMS ether derivatives. The column is especially suited for the quantitation of mixtures containing glucose, galactose, and mannose TMS ethers. Slight variation of the K value for sugars in the hexose and the pentose series may be attributed to anomerization changing the geometry of each chromatographic peak depending on its relative position or retention time. ACKNOWLEDGMENT
We express our gratitude to AUene Jeanes for her encouragement and many helpful suggestions.
LITERATURE CITED
(1) Bishop, C. T., “Methods of Bio-
chemical Analysis,” D. Glick, ed., Vol. X, pp. 1-42, Interscience, New York, 1962. (2) Horning, E. C., Moscatelli, E. A., Sweeley, C. C., Chem. Ind. (London), 751 (1959). ( 3 ) Kircher, H. ,D., “Methods in Carbo-
hydrate Chemmtry,” R. L. Whistler and M. L. Wolfrom, eds., Vol. I, pp. 13-20, Academic Press, New York, 1962. (4) Ray, N. M., J. Appl. Chem. (London) 4, 21 (1954). (5) Richey, J. M., Richey, M. G., Jr., Shraer, R. Anal. Biochem. 9,272 (1964). (6) Sweeley, C. C., Bentley, R., Makita, M., Wells, D. D., J. Am. Chem. SOC. 85, 2497 (1963). (7) Sweeley, C. C., Walker, B., ANAL. CHEM.36, 1461 (1964). JATVAHAR S. SAWARDEKER JAMES H. SLONEKER
Northern Regional Research Laboratory1 Peoria, Ill. 1 The Northern Laboratory is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture. Mention of trade names or companies does not imply endorsement by the Department over others that are not mentioned.
Determination of Boron in Refractory Borides by Pyrohydrolysis SIR: The analytical determination of boron is usually achieved by the separation of the boron from the material being analyzed and the titration of the mannitol-boric acid complex with a standard solution of sodium hydroxide. Several methods to accomplish the preliminary separation have been suggested-e.g., the Chapin Method employing distillation of boron with methyl alcoho! (2); the Blumenthal Method based upon separation of cations by precipitation with a barium carbonate solution (1); ion exchange separation of cations (9) ; separation of cations by precipitation as hydrated oxides; and separation of boron by pyrohydrolysis (IS). More recently i t has been suggested (1.2) that the boron may be titrated in the presence of certain cations by masking the cations with various chelating agents. Most of these methods require that a refractory boride be solubilized, usually by fusion in a platinum crucible with sodium carbonate or in an iron or zirconium crucible with a mixture of sodium peroxide and sodium carbonate. In the case of refractory borides the fusion is often troublesome because of the difficulty of obtaining complete fusion with sodium carbonate or because of the occasional violent reaction of these materials when fusing with sodium peroxide. A high degree of analytical skill is required to prevent significant contamination of the boron solution by
FURNACEP L A T I N U M BOAT
WATER- COOLED CONDENSER
HEATING MANTLE
Figure 1.
I C E BATH RECEIVER
Pyrohydrolysis apparatus
metal ions and loss of boron during the analysis. To circumvent these difficulties it was decided to study the pyrohydrolysis of the refractory borides. Pyrohydrolysis has been used for the separation of boron from glasses (15), boron carbide (8),elemental boron ( 5 ) , plain carbon and low-alloy steels ( I I ) , nuclear reactor materials ( I C ) , and scrap boron-10 materials (6). At the time this paper was being prepared for publication, L. Morgan (IO) reported the successful pyrohydrolysis of zirconium boride. The technique consists of passing steam over the heated sample and collecting and measuring the evolved boric acid. Recent work (6, 8) has suggested that the pyrohydrolysis of boron compounds proceeds in two steps: first, the water oxidation of the boride and second, the transport of the gaseous HBOz or H3B03 formed. The reaction of a metal boride with steam would presumably be the following:
EXPERIMENTAL
Apparatus and Material. An apparatus was assembled (Figure 1) which consisted of a steam generator, a reaction or combustion tube heated by a Globar furnace, a platinum boat to hold the sample, a water-cooled condenser, and a n ice-cooled receiver. The furnace was a Lindberg Model CF-1R Globar unit. The combustion tube (1 inch i.d. X 25 inches long) and the integral delivery tube inch i.d. X 12 inches long) were originally constructed of Vycor glass. To withstand temperatures in the range of 90O0-12OO0 C., a nickel unit was substituted for the Vycor one. Subsequently the nickel unit was replaced with one of quartz. The glass condenser was 21/4 inch and 10 inches long. Steam was generated in a 1-liter, three-neck, round-bottom flask holding about 500 ml. of water and heated by a mantle controlled by a 110-volt Variac. Steam was delivered to the reaction chamber through a 1/4-inch glass tube. A platinum boat was fabricated from 0.003-inch thick platinum foil. The boat was approximately 2 inches long, ‘(4 inch deep, and ‘/z inch wide. This size fits conveniently into a small Vitreosil boat which is used as a support to facilitate the handling of the platinum boat. VOL. 37, NO. 7, JUNE 1965
947
Table 1.
Composition of Metal Borides (In weight per cent)
Total* Total Sample Metal Borona Carbon Nitrogen Oxygen impurities analysis ZrBz 80.50 18.66 0.23 0.03 0.26 0.27 99.95 TiBz 68.50 31.00 0.07 0.02 0.15 0.34 100.08 NbB2 78.87 19.28 0.23
