[HOWE] ISOMERIC PROPYLENE GLYCOLS 15 



the temperature and also the reading on the dilatometer to become 

 constant. The dilatometer was cooled in an evacuated dessicator 

 and weighed; from this the weight of a carefully measured volume of 

 the fat would be obtained. In the case of the distearate of trime- 

 thylene glycol, methyl alcohol, ethyl alcohol, benzol and trichlore- 

 thylene were the constant boiling liquids used to give a series of 

 readings as follows: — 



Trichlorethylene B.P. 87-2°C. Specific Gravity 0-8500 



Benzol " 78-8°C. " " 0-8525 



Ethyl Alcohol « 77-6°C. " " 0-8540 



Methyl Alcohol « 69-0°C. " " 0-8570 



These points were plotted and by extrapolation the specific gravity 

 at the melting point of the fat could be found, which in this case, 

 was 64-7°C., and the specific gravity was found to be 0-8586. 



The following is a detailed description of the preparation of these 

 fats. It was found that the temperature at which the esterification 

 took place was most essential, and the best temperature could only be 

 determined by experiment. 



Stearic Esters of Propylene Glycol 1, 2. The Propylene Glycol 

 (CH3CHOH CH2OH— B.P.188°-189°C.) was esterified with stearic 

 acid at various temperatures from 154°C. to 162°C. for seven or eight 

 hours. The amount of free acid varied from 26-6 — 34-4%. When 

 the temperature was slightly over 160°C. there was less free acid, 

 namely, 16-6%, and a relatively larger amount of ester was obtained. 

 The crystals obtained from these charges were in the form of fine 

 white sheet-like masses. 



The Mono-Stearate so prepared was a pure white crystalline 

 solid, with a melting point of 59-5°C. and a refractive index at 60°C. 

 of 1-4424. These crystals of irregular shape were bright and shiny 

 plates. 



Solubility in 100 grms. of absolute alcohol, 

 at 15°C. 0-034 grms. . 

 at 0°C. 0-021 " 

 The formula CH3CHOH CH2 (C18H35O2) was shown by the following 

 analysis, — 



Saponification value 162-4 % Stearic Acid 82-45 



Theory 163-8 Theory 83-0 



The position of the Stearic acid group, whether 1 or 2 could not 

 be determined as the supply of the glycol was limited. 



Di-Stearate was a white crystalline solid, melting point 72-3°C. 

 and refractive index at 75°C. was 1-4366. The di-stearate formed 

 large crystals, which were very bright and flaky. This was found to 

 be less soluble than the mono. 



