18. MELTING POINTS OF FAT ACIDS. 17 



Mixture of 



Stearic Acid. Laurie Acid. Melts at Manner of Solidification. 



70 30 62-0" Distinctly granular and scaly. 



60 40 59'0" Granular ; commencement of scaly 



crystallization. 



50 50 55'S" Almost amorphous, slightly granular. 



40 60 50 '8 Amorphous, warty. 



30 70 43'4 a On the surface shining faces of small 



crystals. 



20 80 38'5 Amorphous, warty. 



10 90 41-5 Amorphous. 



100 43-6' Crystalline scales. 



Heintz also noticed that a mixture of three fat-acids could melt 

 at a still lower temperature, even if the third fat-acid added 

 possessed a higher melting-point than either of the others. A 

 mixture of 30 parts of palmitic and 70 of myristic acid melts at 

 46-2, and solidifies amorphous. To 20 parts of this mixture 

 stearic acid was added in the following proportions, and melting- 

 point and manner of solidification observed : 



Manner of Solidification. 

 Amorphous. 



To 20 parts of a mixture of 30 parts of myristic with 70 of lauric 

 acid, melting at 35*1, palmitic acid was added, and the following 

 observations made : 



Palmitic Acid. Melts at Manner of Solidification. 



1 33-9' Amorphous. 



2 33-1- 



3 32-2- 



4 327' 



5 33T 



6 34-6' 



7 35-3 

 36-0- 



9 37 '3* Indistinct minute needles. 



10 38-8- Minute needles. 



These tables show clearly that it is important to examine the 

 fractions in the succession in which they were prepared. For 

 instance, supposing the first precipitate to have yielded a fat- 

 acid melting at 68, which might consequently be considered as 

 stearic acid, the following precipitates fat-acids melting at about 



2 



