in concentrations of 100 p.p.m., while platinum, molybdcnurn, and ruthenium interfere if present in excess of about 2 p.p.m. However, the interference by molybdenum may be removed by heating slightly, whereas the rhenium color is stable to heat. Rimshaw (IO) has pointed out that a number of heavy metals such as iron form highly colored complexes with DMG (6),but that these heavy metals can be readily separated from rhenium by precipitation as hydroxides. It is also possible to separate rhenium from many elements by using ion exchange techniques (2) or distillation methods (3).
0 -Triol
I
A
n m
-Triol
0 -TmI
- Pomlr
used I o draw slondwd
CV~YI
17-
161514-
13-
g'
2pi1 -
210. 090 8 -
0 7 .
DISCUSSION
The fact that Beer's law is not strictly obeyed does not invalidate this method of determining rhenium. Ample evidence of this is provided by Figure 2 and Table 11. The nonlinearity of the curve does raise the question of the nature of the color-producing species. Competition between chloro complexes and DMG complexes of rhenium could possibly be the answer. Magee (8) has suggested that complexes may be formed between DMG and lower valent states of rhenium. Mole ratio plots between DMG and rhenium and chloride and rhenium yielded very high results. This suggests that the manner in which the colored species is produced may be rather complex. Nothing more may be said beyond this because of the lack of experimental evidence. Further work in this area should afford a general method for the determination of rhenium. However, since this procedure provided the
04 0 3 0 2 0
IO
20 30 40 50
too
70 P
Figure 2.
I20
150
255
200
P R~e
Standard absorbance vs. concentration curve
means for determining rhenium in standard solutions and thereby satisfied the purpose of this investigation, no further work in this area is being considered at the present time. LITERATURE CITED
(1) Andrew, T., Gentry, C., Analyst 82, 372 (1957'1. (2)-Boyd, G., Larson, Q., J. Phys. Chem. 60,707 (1960). (3) Broda, E., "Advances in R a d b chemistry," p 94-6, Cambridge Universit Press, g e w York, 1950 (4) FadGI, J., Magee, R., Whon, C., Tulunta.4, 17 (1960). \ - - - - , -
( 5 ) Gurvitch, A,, Zhur. ObshcheZ Khim. 27, 40, 316 (1957); C.A. 51, 13635d, 144635 (1957). (6) Hurd, L., Babler, B., IND. ENQ. CHEM.,ANAL.ED.8, 112 (1936). 17) Lazarev. A.. Zhur. Anal. Khim. 14.' . 362 (1959j; C:A. 54,8459b (1960).' (8) Magee, R., private communication, Feb. 15, 1961. (9) Meloche V., Martin, R., ANAL.CHEM. 28,1671 (1956). (10) Rimshaw. 5.. Drivate communication. . Feb. 21, 190i. I
.
Department of Chemistry University of Arkansae B. T. KENNA Fayetteville, Ark. RESEARCH performed under the auspices of the U. S. Atomic Energy Commission.
p-Anisidine-Phosphoric Acid as a Color Reagent for Sialic Acid Compounds on Paper Chromatograms SIR:Many reagents have been used for the detection of sugars on paper chromatograms (I). A preferred reagent is one which gives different color reactions with different classes of sugars, and p-anisidine meets this desideratum (2)* I n recent years the necessity has arisen to distinguish sialic acid and sialic acid-containing compounds from other sugars on paper chromatograms. Benzidine-trichloroacetic acid in aqueous ethyl alcohol has been recommended for that purpose ( 4 ) . However, panisidine-phosphoric acid (2) has been found to be a more satisfactory reagent
for differentiation of several classes of sugars and polyols, and, in the present research, for distinguishing sialic acidcontaining compounds from other sugars. The paper chromatogram is dipped in a solution of p-anisidine (0.5 gram) and phosphoric acid (3 ml. of 85 to 88%) in methanol (100 ml. of 80% aqueous) (2). The paper is blotted to remove excess reagent and heated for approximately 10 minutes a t 105' to 110' C. Sialic acid and sialic acidcontaining compounds appear slowly, giving purplish-gray spots in about 10 minutes. The color of the spots distinguishes sialic compounds from d l
other sugars tested. The background with this reagent is colored pale yellow. Neutral sugars appear after 1 minute a t 105" to 110" C., aldoses as brown spots and ketoses as yellow spots; polyols appear as white spots in 5 to 10 minutes (S). Amino hexoses give brown spots. I n parallel tests the panisidine reagent has proved to be more sensitive than the benzidine reagent for sialic acid-containing compounds because the background is much lighter and the spots are seen more readily. Sialidolactose and sialic acid prepared from bovine colostrum (4, and 6-a-D-sialyl-N-acetylgalactosamine, NVOL. 33, NO. 8, JULY 1961
o
1131
glycolybialic acid, and sialic acid prepared from mucin (3) were among the tested substances chromatographed on filter paper. All these and some other noncharacterized sialic acid-containing substances (sialic acid obtained on hydrolysis) gave purplish-gray spots, which distinguish these compounds from all other sugars tested.
(4)Heimer, R., Meyer, K., Zbid., 27,
LITERATURE CITED
(1) Block, R. J., Durrum, E. L., Zweig, G., “A Manual of Paper Chro2atography and Paper Electro horeais 2nd ed., . 17&214, AcafIemic h e m , New
%k, 1958. Cerbulis, J., ANAL. CHEM.27, 1400
(2)
(1955). (3) Gotpchalk, A:, Graham, E. R. B., Biochzm. et Baophya. Acta 34, 380 (1959).
480 (1968).
J. CERBULIS C . A. ZIITLE
Eastern Regional Research Laboratory’
Philadelphia 18, Pa. ’Eastern Utilization Research and Development Division Agricultural Research Service, U. d. Department of Agriculture.
Extended-Range Hydraulic Mercury Porosimeter Maynard B. Neher, Battelle Memorial Institute, 505 King Ave., Columbus 1 , Ohio BE pressure required to force merT c u r y into the pores of a porous solid is a meaaure of the distribution of macropore sizes (pores with diameters larger than about 100 to 200 A.). The analytical application of this principle waa first reported by Ritter and Drake in 1945 [ANAL.CHEM.17, 782-91 (194511. I n the mercury porosimeter they used, the volume changes which accompany penetration of mercury into a sample are measured electrically in a glaas dilatometer placed in a high-pressure bomb and subjected t o pressures from atmospheric to 15,000 p.s.i. Pressure is applied to the mercury column by compressed nitrogen. Thus, because of safety requirements, this apparatus can be used only in a high-pressure laboratory. Drake has extended the technique to pressures as high as 60,000 p.s.i., which allows determination of pore spectra as low as about 30-A, diameter [Id. Eng. Chem.41,780 (1949)l. The Winslow modification of the mercury porosimeter, produced commercially by the American Instrument Co., Silver Spring, Md., replaces nitrogen as the working fluid with isopropyl alcohol, and the height of the mercury in the dilatometer is observed visually through a glass pressure tube. However, the maximum working pressure is to 6000 p.s.i., and the minimum pore diameter measurable is about 350 A. The pressure-limiting feature appears to be the glass pressure tube. Nevertheless, a hydraulic porosimeter hm decided convenience and safety advantages over the compressed-gas model, especially a t the higher pressures needed to measure small macropores. Therefore, development of a hydraulic porosimeter involving electrical measurement of the mercury height was desirable. Aminco haa recently announced the availability of a 15,000-p.s.i, hydraulic porosimeter, but so far no details of its operation have been available.
1132
ANALMICAL CHEMISTRY
In considering the problem of electrical detection of a mercury-fluid interface, the major unanswered question was whether the fluid used for transmitting pressure would wet the phtinum wire and/or the glass walls of the dilatometer and thus produce incorrect readings of resistance. Atmospheric pressure , experiments established that water or alcohols caused an immediate changa in resistance of the dilatometer, but that saturated hydrocarbons prqduced no change in resistance even after several days’ standing. Neohexane was selected, be-
Figure 1. Dilatometer used for extended range hydraulic mercury porosimeter
cause it is easily removed from the dilatometer, would not cause fouling, and was readily available. However, other saturated hydrocarbons in this molecular weight range should be equally satisfactory. APPARATUS
The dilatometer finally designed (Figure 1) is similar to Ritter and Drake’s. However, for convenience, the sample container (6 t o 10 ml. in volume) waa fastened to the bottom of the dilatometer b a 12/30 standardtaper joint (wale with Apieaon wax).
B
ci
Section A - A
