Polari meter

The use of more complex or more costly articles of equipment, such as catalytic hydrogenation apparatus, autoclaves, polari-meters, ultraviolet absorption spectrometers, etc., has not been described, because the type of such apparatus employed indifferent laboratories varies considerably, and students must be taught the use of their own laboratory equipment. 

In conclusion I desire to thank Dr. J. McCrae, who has written the section on Ethyl Tartrate and the use of the Polari-meter. Dr. T. S. Patterson, who has been kind enough to look over the proofs, and Mr. H. D. Dakin, who has given me substantial assistance in the practical work of revision. 

The use of an automatic polari-meter with a flow-cell has been reported by de Ros il26,to monitor the eluate from an ion-exchange column (Bio-Rad AG1-X2) through which a solution of neomycin was passed. The detection of an optically active substance was recorded electronically with a suitable pen recorder. By determining the areas of the peaks recorded, the amounts of neomycins B and C and neamine in a number of commercial samples have been determined. 

Saccharimeters.—For saccharine solutions use is made of polari-meters with a special graduation, these being termed saccharimeters. 

Imagine you have a sample. A, of an enantiomerically pure compound—a natural product perhaps—and. using a polari meter, you find that it has an [a]D of+10.0. Another sample, B. of the same compound, which you know to be chemically pure (perhaps it is a synthetic sample), shows an [a)o of +8.0. What is its enantiomeric excess Well, you would have got the same value of 8.0 for the Ia]D of B if you had mixed 80% of your enantiomerically pure sample A with 20% of a racemic (or achiral) compound with no optical rotation. Since you know that sample B is chemically pure, and is the same compound as A, it must therefore indeed consist of 80% enantiomerically pure material plus 20% racemic material, or 80% of one... 

The following salts ate determined NH4NO3, NaNOg, NiCl, MgNpg, Chlorates Perchlorates and Other Salts [such as ZnO, Ca(NOg)2, etc]. Sugar, occasionally present, may be estimated either by me dns of a polari-meter or by the Fehling soln method. Usually it is detd by difference... 

Up to now, manually operated polariscopes and polari meters have been the standard method for testing the level of residual stress in glass, e.g. according to ASTM C 148. Polariscopes visualize stress by creating false colors that can be visually compared to reference standards (strain discs or retardation scales) in order to determine the magnitude of stress, but this method is rather qualitative than quantitative and is not suitable for dark and colored glass. 

Specific rotations were recorded with a JASCO DIP-181 digital polari-meter, and absorption spectra were recorded with a Hitachi 100-50 spectrophotometer. H-NMR were recorded with a Hitachi R-24NMR spectrometer (60 MHz) and the C-NMR spectra were recorded with a single contact 75.46 MHz C-CP/MAS NMR method on a Bruker CXP-300 spectrometer equipted with a CP/MAS accessory. 

Although most solid propellants are manufactured in a vertical mixer batch process, a continuous mixing process has been used successfully in the production of the first stage A-3 Polaris propellant and in the NASA 260 inch demonstration motor program. The use of a continuous mixing process, in which propellant chemicals are metered into a helical kneader, offers considerable benefit in terms of safety and cost for large-volume propellant production. 

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