80 



P. 0. Ray— C7*e??izoa? Examination, SjX. 



[ISTo. 1, 



NOTE ON" HtTBL'S IODINE ABSORPTION METHOD. 



There is some difference of opinion as regards the excess of iodine, 

 which should be present after its absorption. Thompson and Ballantyne, 

 who have carefully revised the constants required in the analysis of 

 some fats and oils, are of opinion that " at least double the amount of 

 iodine absorbed should be present." Care was taken to fulfil this 

 condition in most of the analyses as recorded above. On reference to 

 sesame and earth-nut oils, it would appear, however, that it is not 

 always necessary that the iodine should be in large excess. Thus in 

 one case the excess of iodine corresponds to only .5*9c. c N/IO NajSjOj 

 solution, and in another to only 47c. c. Na^SjOj, solution without the 

 results being discoidant. 



For convenieiice of reference the results obtained above are pre- 

 sented below in a tabulated form: — 



Table of constants in the analysis of fats and oils. 



Nature op Fat or Oil. 



Mustai'd oil 

 Niger-seed oil 

 Cocoanut oil 

 Ghee ... 

 Mowa fat 

 Mutton tallow 

 Sesam^ 

 Lard ... 

 Earth-nut oil 



Saponifica- 

 tion equi- 

 valent. 



172-176 



1900 

 258-0 

 218-222 

 199-3 

 199-5-206 

 189-9 

 195-4 

 I960 



Glycerin 

 per cent. 



8-5 

 10-8 



10-5 



Iodine 

 absorption. 



97-0 



120 



6-9 



33-5-39-4 



61-8 



104-5 

 50-0 

 98-0 



SUMMARY AND CONCLUSION. 

 It would thus appear that as the saponification equivalents of niger- 

 seed nil, mowa fat, mutton tallow, sesame oil, lard and earth-nnt oil are 

 very close to one another, their admixtures in considerable proportions 

 cannot be detected by Koettstorfer's test. Even the saponification 

 equivalent of ghee is not far removed from that of lard or tallow. The 

 saponification equivalents of mustard oil and cocoanut oil are, however, 

 highly characteristic. The iodine degrees, on the other hand, afford 

 us valuable hints as to the natui-e of adulteration, the most remarkable 

 featm^e being the exceedingly low numbers for cocoanut oil and ghee. 

 The results of the. application of Reichert's test will be communicated 

 later on. 



