Fast Method Gives Pore Sizes Varied pressure of continuously flowing adsorbate over sample shows size distribution A method to determine adsorption isotherms of porous materials—catalysts, for example—yields size distribution data in about a fifth of the time required by conventional techniques. Developed by A. J. Haley of Engelhard Industries, Newark, N.J., the method involves continuous flow of a nitrogen-helium mixture (having a fixed composition) over a sample. Stepwise variation of the total gas pressure on the sample gives an adsorption isotherm over a wide range of nitrogen pressures. With adsorption data, a pore size distribution is calculated. In other flowing gas methods, thermal conductivity cells used for meas-
uring composition suffer from sensitivity loss. Mr. Haley's method overcomes this problem by keeping the nitrogen fraction of the gas stream constant at 10% or at a level of high cell response sensitivity. Adsorption isotherms are used for calculating pore size distribution in the 10 A. to 300 A. radius range, which is of special interest in catalysis. The conventional pressure-volume methods for determining low temperature nitrogen adsorption isotherms require several days' work by a skilled operator. Isotherms can be developed by the method in six to eight hours, not counting sample preparation.
INCREMENTS. Peaks resulting from incremental adsorption steps are being labeled by Engelhard's A. J. Haley. The method gives size distribution data quickly 40
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More recent flowing stream methods for measuring nitrogen adsorption operate at near atmospheric pressure with varying gas composition. This limits the measurement mainly to surface area because the response from a thermal conductivity cell departs from linearity and loses definition, as the fraction of the adsorbate—again nitrogen—goes up to about 40%, according to Mr. Haley. Pressure Varies. In the new method, total pressure differences with fixed composition change adsorption. In other methods, however, composition differences change adsorption. For example, a mixture of 10% nitrogen in helium at a total pressure of 8 atmospheres has a nitrogen partial pressure of 0.8 atmosphere, equal to a relative pressure of about 0.8 depending on the vapor pressure of liquid nitrogen that's used as coolant for the system. To adjust to a nitrogen relative pressure of 0.3, total pressure over the sample is adjusted to about 3 atmospheres. Consequently, to develop a complete isotherm that is the result of adsorption and capillary condensation, it's necessary to go to about 10 atmospheres. However, while pressure over the sample is varied, the pressure at the point of measurement (the thermal conductivity cell) is maintained at near atmospheric pressure by pressure regulators. In this way, the cell analyzes a 10% nitrogen stream with only small variations in composition due to adsorption or desorption. Mr. Haley assumes that helium is not appreciably adsorbed at above-atmospheric pressure. Thus, assumptions underlying the B.E.T. theory of gas adsorption by finely divided solids and the models used for evaluation of condensation data remain applicable. In making measurements for an isotherm, a sample is first degassed by purging with dry helium and heating to a temperature suitable for drying without changing surface characteristics. After replacing the helium with a mixture of 10% nitrogen in helium, the sample is cooled to liquid nitrogen temperature. The adsorption branch of the isotherm is developed by varying the partial pressure of nitrogen over the sample in suitable increments to approach the saturation point, and measuring the amount of adsorption at the different pressures. At the same time a stream of the gas mixture goes to the reference side of the cell at about
atmospheric pressure. Nitrogen relative pressures are varied between 0.1 and 0.98, Mr. Haley says. This range of relative pressures gives data to calculate pore size distribution of pores from 10 A. to 300 A. radius. In a similar way, the desorption branch of the isotherm is developed by decreasing pressure on the sample in a stepwise manner. Output from the thermal conductivity cell goes to a recorder calibrated for 0 to 40% nitrogen in helium mixtures. Generally, corrections are not needed for variations in flow rates caused by changes in viscosity with changes in nitrogen content. The recorder is set to show a deficiency in nitrogen caused by adsorption as a peak. When adsorption equilibrium is established at a given relative pressure, the peak area is measured and converted to volume of gas adsorbed per unit weight of sample. At increased relative pressure, a subsequent peak equals the incremental pressure increase. Total adsorption at the new pressure is equal to the sum of the adsorption peaks. Some operating experience helps in predicting the shape of the peaks so that adjustments can be made to compensate for extreme changes in adsorption, Mr. Haley explains. Peak height and width can be modified by changing the signal from the conductivity cell and by changing chart speeds. Reproducibility of the method is good, Mr. Haley says. Pore size distribution results and surface area measurements compare well with measurements by conventional methods, such as the pressure-volume method. Engelhard has patents pending on this method of finding pore size distribution. The company expects the instrument to be commercially available in the near future.
# 1 of a series by Ultek Corp., sole manufacturer devoted exclusively to ion pump technology
QUESTION: How do you make an electronic vacuum cleaner?
ANSWER: Make sure you use an Ultek electronic vacuum pump.
The cleanest vacuums this side of outer space (and maybe even cleaner
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Diazonium Compounds Give New Aldehydes More evidence extends the use of a new aldehyde synthesis in which diazotized sulfanilic acid cleaves asubstituted p-dimethylaminobenzyl alcohols to make aldehydes. The technique has given 11 additional aldehydes—aromatic, saturated aliphatic, and unsaturated aliphatic. The reaction is convenient for the preparation of moderate quantities of aldehydes (0.2 to 0.4 mole) in good yield and high purity, according to
niques, and avoids contamination in such critical applications as surface friction studies, thin film deposition, altitude simulation, photo-sensitive surface studies, and vacuum tube processing. W e ' d like to tell you more; write today for details. Send for free booklet
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d e t a i l s the e s s e n t i a l facts a b o u t ion pumps in general a n d Ultek ion pumps in particular. CORR Uliek ion pump
920 Commercial Street Boston
New York
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Palo Alto
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Los Angeles
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Washington, D.C.
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NOW AVAILABLE... PACKAGED WITH COMPONENTS THE ASCO "50-2P" ROTA-FILM MOLECULAR STILL for convenient assembly and quick operation ! • includes: (1) 2 " Still complete with type #316 stainless stee! rotor and wiper retainer, heating mantle (340 watts) (2) 500 ml receiver flasks, teflon wipers, continuous feed flask with teflon needle valve. For 115V, 1 phase, 60 cycle power. (1) 1 " Oil Diffusion pump, 135 watts, 115V. (1) Dry Ice Trap, 3 " dia. x 10" lg., with 29/42 joint. (1) Dry Ice Trap, 3 " dia. x 10" lg., with 34/25 ball joint. (1) Mounting Platform with all mounting clamps, electrical outlets and switches. Total Price •
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ARTHUR F. SMITH, INC. • 311 ALEXANDER ST., ROCHESTER 4, N. Y.
ABEX
a new series of anionic surfactants
Dr. Anthony Sisti of Adelphi College, Garden City, N.Y. Dr. Sisti and coworkers JuMa Burgmaster and Murray Fudim say the method works equally well for making aliphatic, aromatic, and unsaturated aldehydes. And it's relatively unaffected by steric or electrical effects in the aldehyde group [/. Org. Chem., 27, 279 (1962)]. Previous workers focused their attention on the reaction's noncarbonyl product, the azobenzene derivative. The carbonyl product was seldom isolated and characterized. Dr. Sisti and Dr. Martin Stiles of the University of Michigan were first attracted to the method's possibilities for making aldehydes at Michigan, when the reaction emerged in the form of a molecular rearrangement. Diazotized sulfanilic acid cleaves the ce-substituted p-dimethylaminobenzyl alcohols at p H 5 to 6 at 0° to 5° C. The diazonium salt provides the necessary electrophilic reactivity and allows easy removal of the methyl orange by-product because of methyl orange's insolubility in ether. Reaction conditions are ideal for handling sensitive aldehydes. Ether extracts of the reaction mixtures contain nearly pure aldehydes. Reaction yields range from 50 to 82%. To obtain maximum aldehyde yields, the dimethylaminobenzyl alcohols should be isolated and purified before they enter the cleavage reaction, Dr. Sisti says. The Adelphi group has extended the reaction to make such aldehydes as 4-methoxybenzaldehyde, 2-methylbenzaldehyde, 5-hexenal, heptanal, and /?-phenylcinnamaldehyde.
Scandium's Properties Resemble Yttrium's
typical properties
• Exceptionally Low Foaming • No Cloud Point up to the Boil • Fluid below 0° C • No Deactivation by Metal Ions • Not Precipitated by Cationics • Soluble in Concentrated Salt Solution • Stable Over a Wide pH Range
Samples and literature available upon request.
®
Registered Trademark, Patents Pending
Alcolac Chemical Corporation 3440 FAIRFIELD ROAD • BALTIMORE 26, MARYLAND • ELGIN 5-2600 44
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Analysis of the first pound of scandium ever made shows that the rare metal has mechanical and physical properties similar to yttrium, and somewhat similar to titanium. The analysis was made by Doyle Geiselman of UCM (division of Union Carbide Corp., New York). Earlier, a pound of scandium was made by UCM for the Air Force. The tests just completed on the metal include: • Crystal structure and density. • Electrical resistivity, thermoelectric power properties, and thermal expansion.
• Hardness, modulus of elasticity, and tensile and compressive strengths. • Corrosion resistance and reactivity with air, nitrogen, and oxygen. UCM's conclusion is that scandium resembles yttrium and the rare earth metals more than it does aluminum or titanium. In fact, UCM says, research conducted on yttrium might serve as a guide to scandium's behavior.
which product will pass the sniff test?
BRIEFS A new primary diesel reference fuel— 2,2,4,4,6,8,8 - heptamethylnonane—has been proposed by the National Bureau of Standards. It would replace 1-methylnaphthalene, the present lowcetane standard that's used to determine diesel fuels' ignition quality. The proposed standard (which wouldn't change the cetane number of commercial diesel fuels) is easily made by sulfuric acid dimerization of diisobutylene. T h e method gives three olefin hydrocarbons in the C 1 6 range that are hydrogenated to the proposed standard.
Proof of a lethal toxin produced by the blood of an animal as a result of a burn or scald has been established, says Dr. Alfred B. Chaet of American University, Washington, D.C. Work done at American and at the Marine Biological Laboratory, Woods Hole, Mass., shows that injecting blood of scalded fish (Fundulus) into healthy ones kills about 5 1 % of the healthy specimens. Fatalities run as high as 8 5 % in similar experiments done with star worms, marine worms, and crayfish. Nature of the toxin, how it works, and how it's produced aren't known, Dr. Chaet says. The important thing, though, is that the toxin is fatal to injured and healthy animals.
it could be yours... With so many look-alike, do-alike products on the market, the odor factor has become of major importance in imparting an air of distinction and creating repeat sales. To give a product the elusive "scents of sell" is the job of an Odrene*, Sindar's specially compounded fragrant additives. Today, thanks to the Odrene additives, countless brands of waxes, cleansers, polishes, paints, etc. gain an extra measure of sales success. The Odrene additives are easy and economical to use . . . versatile in application . . . and available in a wide range of unique odor types, making it possible for your product to be distinctly different. Will your product pass the sniff test? Send us a sample; our laboratory will insure that it does.
The importance of virus infections in mental retardation, Mongolism, cerebral palsy, and other neurological disorders is under study at the National Institute of Neurological Diseases and Blindness and the National Institute of Allergy and Infectious Diseases. Blood samples from over 75,000 expectant mothers are being used to study how viruses may b e implicated in the diseases, with which infants are sometimes born.
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FREE! Send for the Sindar Reporter . . . our house publication that discusses the odor factor in detail for industrial products and problems. It's filled with important technical and marketing information that could be vital to your manufacturing and selling program. Receive it regularly without obligation. Write today.
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