124th NATIONAL ACS MEETING
A field installation for determining the SOj a n d SOs content of flue gas is checked by Efc. E . Matty, Babcock a n d Wilcox to which the phototube output and a voltage corresponding to the position of the scanning l>eam on the column are applied, produces a pattern which changes with the ultraviolet reflectance of the column. Chromatogrom Scanning. Paper chromato> grams of radioactive substances may be s c a n n e d automatically by an instrument described by VVillian N.-e, Stanford University. T h e paper strips are mounted on Lucite strips which are advanced under a windowless gas-flow Geiger-Muller tube. The location of t h e radioactive spots is readily ascertained through the use of a rate meter and. recorder, or a scaler. The drives for advancing t h e strip and the shutter of the Geiger-Midler tube are coupled together. The disposable Lucite strips minimize the danger of contamination of a strip with radioactivity from a previous strip, said Dr. Nye.
^ Oxygen ira Hydrogen Oxygen present in hydrogen in concentrations a s lo"w as 1 to 100 parts per million is quantitatively determined by a procedure of VI. M. Wright, Consolidated Mining a n d Smelting Co. of Canada. The oxygen is converted into water vapor by means of a platinum catalyst. A liquid nitrogen cold txap condenses the water, the volume of which is measured under vacuum (10 win- of mercury). Great care must he taken to ensure accuracy when performing this test; adsorption of the water on the glass apparatus must be considered in calibrating the equipment. Accuracy at the lower limit of the method is lO'/r, but a t 20 parts per million the accuracy is in* the neighborhood of 2 ' , Y , Dr. W r i g h t said. C a r b o n anc3 Hydrogen. T h e lead peroxide which is used in the combustion tube
385^
filling in t h e Pregl microdetermination of carbon and hydrogen has been successfully eliminated in a method developed by George F. W r i g h t a n d C. K. Cross, both of the University of Toronto. A mixture of. trihydroxylamine phosphate a n d asbestos is used between t h e water a n d carbon dioxide absorption tubes to remove the higher oxides of nitrogen. One rilling of the t u b e is good for 250 analyses, said Dr. W r i g h t . A shrinkage in the tube indicates exhaustion. Dextran. T h e anthrone reaction, which is gaining in popularity ior analyzing carbohydrates, has been adapted to the determination of dextran by Troy A. Scott, Jr., Northern Regional Research Laboratory. T h e greatest source of error in the method is t h e variation in t h e blank used when the green color is measured in the spectrophotometer. By carefully standardizing the t e m p e r a t u r e and reagents, the standard deviation of the analytical procedure can b e reduced to 0 . 4 8 % a t an optical density reading of 0.600. Moisture on Uranium. Adsorbed or combined moisture on uranium or uranium oxide is not readily detected by the usual moisture procedures such as the Karl Fischer method. However, James O. Hibbits, Carbide and Carbon Chemicals, Oak Ridge, determines moisture in these substances b y heating samples in the conventional t u b e furnace and conducting the moisture away from t h e t u b e by a stream of nitrogen, absorbing it, a n d then titrating using a dead-stop e n d point technique. Analyses by Dr. Hibbits indicate that t h e moisture adsorbed on uranium
oxide ordinarily a m o u n t s to about 0 . 0 2 % . However, if the oxide is prepared from uranyl sulfate, t h e moisture content is about 0 . 1 % . Dr. Hibbits said that he saw -no reason w h y this method could not be used for other types of samples provided they d o not decompose to form water when heated. C a r b o n in Na-K Alloy. Carbon contained in sodium-potassium alloy, w h i c h is widely used as a h e a t exchange fluid in nuclear reactors, can seriously d a m a g e t h e steel of w h i c h such equipment is constructed, said K. G. Stoffer, Babcock & Wilcox. In principal, t h e ordinary method of microcombustioii in oxygen can b e applied to the sodium-potassium alloy; however, several properties of t h e material raise a number of difficulties. T h e reactive n a t u r e of the alloy necessitates sampling in an inert atmosphere. A suitable device for doing this has been built b y Mr. Stoffer and J. H. Phillips, w h o is also with Babcock & Wilcox. Nitrogen is the inert gas employed. O n c e a sample is taken and allowed to harden, the entire sample must b e analyzed since there m a y be segregation and precipitation of dissolved materials on cooling. A further difficulty stems from the rapid ignition which occurs when t h e sample is exposed to oxygen. Unless t h e oxygen is J'ed into the apparatus at a temporarily high rate ac the m o m e n t of ignition, liquid from the adsorbers will be drawn back into t h e combustion t u b e , said Mr. Stoffer. S a m p l e size used was on t h e order of 100 nig; t h e average deviation of the m e t h o d is about 0 . 0 0 5 % .
DIVISION OF CARBOHYDRATE CHEMISTRY
Nuclear Magnetic Resonances Used In Moisture Determining Techniques • First chemical synthesis of sucrose m a y biochemists in tracing path of s u g a r in life processes • R a d i o a c t i v e tracers p r o v i d e photosynthesis studies of sugar c a n e
basic
data
aid in
• I m p r o v e d hydrolysis a n d f r a c t i o n a t i o n t e c h niques increase yields of clinical d e x t r a n to 4 7 % **TpHE nuclear magnetic resonance tech"•• nique is potentially useful for determining t h e degree of hydration of sugars, the relative amounts of bound and free water in hygioscopic solids, a n d possibly the relative amounts of bound and free fat. Development of the equipment and procedures for moisture determinations utilizing the phenomenon of nuclear magnetic resonance was described in two papers by William L. Roliwitz and John P. O'Meara
CHEMICAL
of t h e Southwest Research Institute, presented before the Division of Carbohydrate Chemistry as part of their joint symposium with the Division of Analytical Chemistry on t h e analytical methods and instrumentation applied to sugars and other carbohydrates. In 1950 Shaw and coworkers at the Western Regional -Research Laboratory inv estigated t h e use of t h e nuclear resonance technique to determine the moisture con-
AND
ENGINEERING
NEWS
CARBOHYDRATE CHEMISTRY tent of hygroscopic solids and iound a definite, almost linear relationship b e t w e e n the magnitude of the absorption signal from the hydrogen nucleus a n d the a m o u n t of moisture present. T h e s e results, a c cording t o the authors, p l u s the fact that the technique needs no s a m p l e modification and the rapidity w i t h which measurements can he made p r o m p t e d them to develop t h e theory a n d design t h e e q u i p m e n t for obtaining moisture determinations by m e a s u r e m e n t of proton n u clear magnet resonance absorptions. Their t e c h n i q u e can g i v e information on the n u m b e r of nuclei as well as about t h e nuclei a n d its e n v i r o n m e n t . T h e nucleus can be considered as a s m a l l bar m a g n e t . In t h e a b s e n c e of an external field, these nuclear magnets will b e oriented in a random fashion a n d will give a very small resultant magnetic field w h i c h would b e too small to measure. However, when t h e s e magnets are placed in a m a g n e t i c field, t h e y tend to orient themselves with the field and give a l a r g e r p a r a m a g n e t i c effect. A d e q u a t e signal strengths, which can be o b t a i n e d a t m a g n e t i c fields in d i e neighborhood of 2J50 g a u s s , allow routine measurements of m o i s t u r e content a b o v about 9
