AN INVESTIGATION OF THE USE OF RADIOACTIVE ISOTOPES FOR DETERMINING THE SURFACE AREA OF POWDERED MATERIALS BY SORPTION METHODS. Quarterly Technical Status Report No. 4 covering Period: April 18 1960 to June 30, 1960
The technique developed in this project for surface-area determinations by radiostearic acid sorption was examined to determine the simplest sample- drying technique, the minimum sample-drying time, and the minimum sorbatesorbent contact time that would be adequate for most types of powders. Samples of several powders (zinc sulfide, alumina, titania, sodium carbonate, and sodium bicarbonate) were dried by one of the following methods before determination of their surface areas: (1) in an oven at 11O/sup o/C and atmospheric pressure; (2) in a vacuum oven at 120/sup o/C and 100 rum Hg; and (3) at 100/sup o/C and 100 mm Hg in a sample flask with a stopcock for adding the stearic acid solution without admitting air to the dried sample. Several different drying times were also compared. It was found that an inert powder such as zinc sulfide can be sufficiently dried in 2 hr at 110/sup o/C and atmospheric pressure. Basic powders, such as sodium bicarbonate, can react with stearic acid if traces of moisture are present, but they must be dried at low pressure in a flask (as described above) designed to exclude air from the dried sample. Materials with a great affinity for water must likewise be dried at reduced pressures and protected from contact with the atmosphere. Experiments designed to compare different times of contact between the dried sample and the stearic acid solution indicated that 1 hr is sufficient time to reach sorption equilibrium within the limits of experimental error. I am experiment comparing the sorption of stearic acid, C/sub 18/H/sub 36/O/sub 2/, with the sorption of lauric acid, C/sub 12/H/ sub 24/O/sub 2/, on porous charcoal powder (with a BET value of 400 m/sup 2//gm), the fatty acid sorption values for surface area were 61.7 and 63.6 m/sup 2//gm, respectively. Apparently the shorter acid molecules could not penetrate the pores of the powder any better than could the longer ones. (auth)
- Research Organization:
- Georgia Inst. of Tech., Atlanta. Engineering Experiment Station
- DOE Contract Number:
- AT(38-1)-202
- NSA Number:
- NSA-15-004207
- OSTI ID:
- 4116023
- Report Number(s):
- TID-6978; Project No. A-446-3
- Resource Relation:
- Other Information: Project No. A-446-3. Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- United States
- Language:
- English
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