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
Mercury reservoir
Tygon tubing
Screw clomp
10,000
IPOO
5,WO
100
500
Scale I
Pore Dlamslrr A.
I in
Figure 2. Filling adapter for dilatometer
The platinum wire (32-gage) was brought through the wall of the enlarged upper portion with cobalt-glass seals, one lead above the other. They were bent over so that the lead wires emerged from the seal parallel to and within l/, inch of the enlarged portion of the dilntomctcr tube, and soft-soldered to hravicr leads which were fastened to a rigid Bakelite mounting block to minimize dan er of breaking the platinum wire) andyor cracking the glass seals The mounting block, A-A of Figure 1; was fastened to the glass tube by a strip of shect brass (not fihown because it would interfere with other details), which encircled both the glass tube and the Bakelite mounting block. On the inside of the dilatometer, the platinum wire was strung from the lower seal straight down the wall of the dilatometer capillary, over a glass rod sealed in the enlarged tube just below the capillary, and returned up the opposite wall. A loop was formed near the other m d of the platinum wire, and the end of the wire was sealed in the upper cobalt-glass seal, with slack left on the wire inside the dilatometer. Tension was applied to the platinum wire by a screw-actuated mechanism shown in side view in the enlarged section of Figure 1, and shown in front view in A-A, Figure 1. This mechanism consisted of a stainless steel machine s o r w (No. 4-40, 2 inches long) held in a slotted Plexiglas frame. A movable piece of Plexiglas which fitted loosely in the slot was threaded to receive the 4-40 machine screw. The loop in the platinum wire was hooked over a protrusion on this movable piece, and as the machine screw was turned clockwise, the movable piece of Plexiglas section moved upward and applied tension to the platinum wire. Sufficient tension was used to straighten the wire, but cart' was taken not to stretch it sufficiently to develop thin spots. The screw-actuated mechanism was supported on a glass hook protruding from the glass wall of the dilatometer op osite the cobalt-glms seals and '/E inch gelow the spherical glass joint.
Figure 3. Comparative pore volumes of a commercial alumina using conventional mercury and extended-range hydraulic mercury porosimeters
The dilatometer was filled with mercury by use of the adapter shown in Figure 2.
The dilatometer was attached to the adapter by means of the 35/45 ball joint on the bottom of the adapter, and the dilatometer and adapter were then evacuated. Mercury, was admitted to the dilatometer, while it waa still evacuated, through the mercury reservoir on the adapter. The mercury reservoir was attached by means of Tygon tubing and a screw clamp rather than a stopcock to avoid contamination of mercury by stopcock grease and possible fouling of the platinum wire in the dilatometer. After the vacuum was released, the dilatometer was disconnected from the filling adapter, the space above the mercury column was filled with neohexane to the top of the spherical joint, and a 3-inch-square piece of thin gum rubber (dam rubber) was placed over the joint and held in place by 1-inch-long sections of 1-inch Gooch rubber tubing around it. The dilatometer was placed in a 15,000-pound high-pressure bomb, and the two leads were brought through an insulated lead in the bomb head. The bomb was filled with ethylene glycol and pressure was supplied with a handoperated high-pressure pump to a maximum pressure of 15,000 p.s.i. (Autoclave Engineers, Erie, Pa.). The 15,OOO-p.s.i. limit was imposed by the equipment available. In principle there is no reason why this technique could not be used to much higher pressures, possibly 100,000 p.s.i. or higher. Fksistances were measured with a Wheatstone bridge to the nearest 0.001 ohm. The apparatus was used in a constanttemperature room, and with the good thermal conductivity of the liquid-filled system and the high heat capacity of the massive autoclave, thermal effects due to electrical heating of the platinum wire were negligible. Ethylene glycol was chosen as a pumping fluid primarily because it is easily removed by washing with water.
In theory a hydrocarbon could be used as both pumping fluid and aa the fluid in contact with the mercury column. However, direct pumping at high pressure of light hydrocarbons, such aa neohexane, is difficult because of their very low viscosity. Hydrocarbons of higher molecular weight which are sufficiently viscous to be pumped easily at high pressure cause difficulty with fouling of the platinum wire. Thus, the two-fluid system waa selected as the simplest approach. RESULTS
With the hydraulic porosimeter assembled, LI blank run was made (Table I). A linear, repeatable, and reversible increase in resistance with increasing pressure was found, which could be accounted for by the compressibility of mercury and glass. Since the change in resistance was repeatable (within 0.001 ohm), linear, reversible, and explained by compressibility data, this was taken m verification of the basic expectation that a hydrocarbon solvent would not interfere with contact between mercury
Table 1.
Data for Hydraulic Porosimeter Blank Run.
Pressure, Reading P.S.I.G. 0 15,000 0 5,000 10,000 15,000 15.000 15:000 151000
10
n
0.517 0.528 0.517 0.520 0.523 0.528 0.527 0.527 0 527
11 12
15,000 0
0.527 0.517
8 9 ~.
a
Resistance Resist- Change, ance, Ohm/1000 Ohm P.S.I.G.
n
517
0 O.OO07 0 O.OO06 0.0006 0.0007 0.0007 0.0007 0.0007
n
0.0007 0
5-ml. sample bolder.
VOL. 33, NO. 8, JULY 1961
1133
and the platinum wire. Accordingly, this change of resistance was used as a correction factor in actual pore-spectra determinations. To compare the extended-range hydraulic porosimeter with the conventional Ritter and Drake porosimeter which had been in use in this laboratory
for some t i e , the pore spectrum of a commercial alumina (spherical form) was determined using both instruments. The results, shown in Figure 3, show remarkably close agreement for the two methods, and indicate that the new instrument gives resulte comparable to the conventional mercury porosimeter.
Since the sample was R commercial alumina on which virtually no other information was available, any deduction a.bout the meaning of the data would be potentially erroneous. Drake and Ritter and Drake discuss the interpretation of pore distribution determined by mercury penetration.
Microvalve and Connector for Automatic Column Chromatography Eric Schrarn' and Robert Lornbaert, Faculty of Medicine, University of Brussels, Brussels, Belgium et al. (4) have shown that S in the automatic chromatography of amino acids, mixing of the effluent PACKMAN
may be avoided by keeping the diameter of the liquid stream sufficiently small--e.g., approximately 0.7 mm. Therefore, all connectors and valves placed in the line should be of the same inner diameter and should remain watertight under sometimes rather high working pressures. Moore et aE. (1) have used B Teflon microvalve. The device described here is a similar valve, used in our laboratory for nearly a year.
-
1 Present address, Chercheur A r.66 de 1'Institut Interuniversitaire des ffciencea Nucl&irea, Brussels, Belgium
1cm.
Figure 1.
b
Connector for Teflon capillary tubing
C
Figure 3, valve
to analyzer
Detail of Teflon micro-
from column
u----v 2!!A
Figure 2.
Teflon rnicrovalve
For more cleorness saews have not all been represented
1134
6
ANALYTICAL CHEMISTRY
to control panel
