with buffer solutions is only partly affected by differences in structure.The low isoelectric point of fibroin (pH 2.2), although somewhat striking, is easily accounted for with a little knowledge of the structure. That the fibroin molecule contains an excess of free carboxyl groups over free amino groups has already been pointed out. Toa (5) demonstrated that fibroin was a negative colloid in aqueous solution and in an electrical field would migrate toward the anode. These observations are also confirmed by the fact that basic dyes form more stable combinations with silk than acid dyes.Literature Cited (1) Hardy,

Measurement of pH for Solutions of CFa(CHa)aCOaH, CFa(CH2)aCOaH, CHa (CHa)aCOaH 57 IX.

The theoretical investigation of time-dependent quantum systems requires the solution of the time-dependent Schrödinger (Dirac) equation. We present a formalism which enables the generation of an optimized set of pseudostates based on a decomposition of the Hilbert space into a hierarchical structure of finite subspaces. To illustrate the method we present results for a simple interatomic collision problem.

the cooling which is preliminary to carbonation. By so doing, the yield is improved because otherwise oxygen from the atmosphere would be pulled in and react with the Grignard reagent. In a 0.2 mole run the yield of cyclohexanecarboxylic acid based on an 80% yield of cyclohexylmagnesium bromide was 83%; and the yield of acid based on a 92% yield of cyclohexylmagnesium chloride was 93%. It is recommended that the solution be diluted with ether (300-500 cc. in a 0.2 mole run) prior to carbonation, because of the sparingly soluble salt (RCOOMgBr) which is formed. Summary Cyclohexylmagnesium chloride and bromide can be prepared in excellent yields. In its reaction with magnesium, bromocyclohexane differs significantly from other secondary bromides. General recommendations are given for the use of RC1 in preference to RBr and RI compounds for the preparation of Grignard reagents.

No abstract