INDUSTRIALAND ENGINEERING CHEMISTRY 473 nated rubber, the solvent strength as measurd by the dilution ratio is of considerable importance.2. The compatibility of blown castor oil with chlorinated rubber, some other blown oils, and some alkyds, is dependent upon the strength of the solvent used. Strong solvents as measured by their dilution ratio enhance compatibility.3. No particular plasticizer is best for use with chlorinated rubber. Different plasticizers impart totally different results at different loading percentages. The choice of plasticizers will be dictated by the ultimate properties desired. More frequently than not, the use of two or more plasticizers will be necessary to obtain the optimum properties for any given application. 4. Consideration of the fundamental principles and trends presented in this paper will be helpful in the formulation of chlorinated rubber finishes for a wider variety of uses, and products of an improved nature will be the result.

The physical test data for 40-, 60-, and 90-minute cures at 259" F. of stocks exposed to these conditions are shown in Figure 7. This chart indicates an increase in the rate of cure due to an increase in humidity, but little change in optimum physical properties.It is apparent from this investigation and the work of the Carbon Black Komenclature Committee on GR-S compounds, as well as from data on natural rubber, that the presence of moisture has an influence on the rate of cure'which cannot be ignored; considerable attention, therefore, should be given to conditions during testing when working up specifications for evaluating GR-S compounds. The work on natural rubber involved other accel-erators than thiazoles, however, and data with stocks using di-otolylguanidine a~ accelerator showed a retardation of cure rather than an acceleration due to increase in moisture content. This would indicate that further work should be done along this same line to find the effect of other types of acceleration. LITERATURE CITED(1) Braendle, H. A,, and Wiegand, W. B., IND. ENQ. Cmnx., 36, 724(2) Hall and Rall, ORD Report (1944).(3) Physical Testing Comm. Div. of Rubber Chem., A.C.S., Rubber (1944). Methyl AcetoxyEFFECT HE pyrogenic transformation of a lactic acid derivative (4, 17, 18, 19),

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