(87) 



itself — the determination of I he binary nieltingpoint-line must be 

 reckoned fiinh}- as soon as it is to render quantitative services, whicli 

 is of importance for the analysis of butter ; for if the meltingpoint- 

 curve is accurately known, the cpiantity of phytosterol added may 

 be calculated from the elevation of the melting point of the cholesterol 

 acetate. I have, therefore, now determined the binary melting point 

 line in the proper manner. (Fig. 4\ 



a:.'' 



/Ji7 



too 



fOO 



90 



60 TO. 3/0 



bO 



JO 



20 



fP 



50 ^Z-^ 



Fig. 4. 

 Cholesterol-, and Phytoslerol-Acetate. 



Altliongh the curve takes an upward course it still deviates con- 

 siderably from the straight line which connects the two melting- 

 points. As the course of the curve from 40 7o cholesterol-acetate to 

 7o is nearly horizontal, it follows that the composition of mixtures 

 can be veritied by the melting-point, when the admixture of phytosterol 

 in the animal fat does not exceed 60 "/o. The results are the most 

 accurate when the quantity of phytosterol-ester^) amounts to 27o — 'AOVo- 

 In practice, this method is therefore applicable in most cases. The 

 cholesterol-acetate used in these experiments melted at 112. °8; the 

 phytosterol-acetate at 129.°2. 



A mixture of 90 «/^ Choi. Acet. -f 10 7„ Phyt. Acet. melts at 117° 



+ 20 .) 



+ 26.7 » 



-j- 40 » 



+ 57.6 )) 



4- 80 » 



+ 90 » 



120.°5 



122. °5 



125° 



128° 



129.°1 



129.°2 



1) It should be observed that although Bomer, in several parts of his paper, 

 recommends the said method for qualitative purposes only, it is plain enough in 

 other parts that he considers the process suitable for (juantitative determinations 

 in the case of small concentrations. In his interpretation of the melting point line 

 this is, however not the case, for his experiments give no explanation as to the 

 mixing proportion of the components in mixtures of definite observed melting point. 

 Quantitative determinations are only rendered possible by a complete knowledge of 

 the binary melting point line. When the concentration of cholesterol-acetate is 

 0,5 — 1"/,,, the meltingpoint is practically not altered ; when it is 2"/,, however, 

 the amount is easy to determine. 



