A kinetic study was made of the reaction of steam and natural gas over a reduced nickel catalyst at a temperature range of 637" to 1,180"F.The rate of reaction is first order with respect to methane. T h e present study is concerned w i t h t h e determination of t h e effect of t h e composition on the rate of reaction of steam and natural gas on a reduced nickel catalyst at a temperature of approximately 1,180"F. and 1 atm. pressure. APPARATUSA diagram of the apparatus is shown in Figure 1. In order to facilitate the description of the apparatus, i t will be considered as in operation.Distilled water was fed from a constant-head source through a needle valve and a capillary orifice into the preheater, which consisted of a 1-in.pipe containing porous-clay chips ; the pipe was inserted in a small electric furnace. The natural gas passed through a dry test meter to a small compressor equipped with a needlevalve by-pass arrangement. The compressor was operated only a t high flow rates. The steam from the preheater then mixed with the natural gas and was admitted directly into the reactor.The reactor consisted of a piece of 2-in. pipe with a welded connection at the upstream end and a blank flange at the downstream end inserted in a 2-kw. electric furnace. Passing through the blank flange was a %-in. pipe to which was welded a small cup fitted with a screen upon which the catalyst was placed. A 1/4-in. steel tube was also inserted in the blank flange t o serve a s a thermowell. A chromel-alumel thermocouple was placed in the thermowell immediately above the catalyst bed and a second thermocouple was placed in the center of the screen on the same level a s the single layer of catalyst.Upon entering the reactor the gases passed from the 2in. pipe downward through the catalyst bed and out the I/s-in. pipe to a watercooled condenser. The condensate was removed continuously by a U-tube drain and weighed. The saturated product gases passed on through a sampling cock and then to a wet test meter.The arrangement of the catalyst in the reactor was unique in that radiant heat supplied the energy necessary for the highly endothermic reaction. The catalyst bed was approximately 1.5 in. wide and 3.5 in. long. The bed was centered in the 2-in. pipe which formed the reactor wall. Thus the catalyst was exposed t o radiant heat on all sides. It is believed that temperature variation in the bed was a t a minimum. A.1.Ch.E. Journal EXPERIMENTAL PROCEDUREAfter the condenser and the thermocouple leads were disconnected, the flange was uncoupIed and the catalyst assembly was removed from the reactor tube. A weighed amount of catalyst was placed on the screen. The area of the screen opening was varied by the use of sheet metal so that the catalyst completely covered the open area with a single layer. The catalyst assembly and connections were then placed back in the reactor.The reactor then was brought up to temperature and the feeding of water begun. The water feed rate was adjusted prior to the introduction of the gas. For a series of r...

SummaryMaximum extraction stress and integrated extraction work were measured for sutures implanted for 3, 7, and 14 day periods. Six common non-absorbable sutures, representative of braided and monofilamentary forms, were implanted subdermally and were used for cutaneous incision closure with purebred pointer dogs. The data show: ( 1 ) Braided sutures, polyester/Teflon, silk-type B, and silk-silicone interacted with peripheral tissue to a significantly greater degree than the monofilamentary types, nylon, polypropylene, and polyethylene; ( 2 ) polyester-Teflon braided suture interacted to a lesser degree than the other braided sutures; (3) the relatively intense interaction of plain silk and siliconetreated silk appears to reflect the combined effects of mechanical aspects of braiding and of biochemical response; and (4) all braided sutures swelled over the implantation periods with as much as a 70% increase in diameter after 14 days for silk.

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Low concentrations of substances having a lower surface tension than oil romote foaming markedly in oils if a single phase is present. If two phases are present and the added phase is finely dispersefin the oil the substance is a strong anti-foamant.Photomicrographs and high-speed motion pictures present a visual confirmation of the mechanism of anti-foamants. IntroductionFoaming and the control of foaming in gasliquid systems represents an area in which few quantitative relations have been developed. Since both static and dynamic properties represent major system variables, precise experimental measurements necessary for theoretical analyses are extremely few. This experimental study, largely qualitative in nature, attempts t o elucidate the mechanisms of foaming and foam stability, and hence provide a sound basis for theoretical attack.Four oils, designated as 555, 702, 528 and 529 and having quite different physical properties and foaming characteristics were chosen as subjects for the study. Dow-Corning 100 C.S. and 1000 C.S. silicones were used as anti-foamants.Foam Studies I n order to evaluate the influence of temperature, physical properties of different oils and concentration of silicone on the foaming properties of the oils, a series of foam tests were carried out in which a measured volume of oil was aerated by nitrogen flowing a t a fixed rate through a porous stone. The temperature was maintained at a desired level by flowing liquid through the jackets of the oil containers. If silicone was to be added, a solution of silicone in n-pentane (0.1%) was added to the oil while stirring in a special high-speed stirrer. The results of these measurements are recorded here.Oil 528.-Samples containing 0, 0.5, 1.0, 2.0, 2.5, 5, 10, and 20 p.p.m. of silicone were aerated over the temperature range of 20 to 120". At 20", none of the samples produced foam; however the bubbles were much smaller than in those with silicones (0.5-3.0 mm., in diameter as compared to 5.0 mm. with silicones). At 60", the sample without silicone began foaming. At 70", the 0.5 p.p.m. sample began t o foam. The number of bubbles floating in the liquid decreased and the size of the bubbles increased with increasing silicone content. At 97" small bubbles began collecting on the surface of the