1 66 MILK AND DAIRY PRODUCTS PART 



a lower temperature than 116 (corrected m.p.) there is a possi- 

 bility that vegetable fat has been added. When the ester melts 

 only at 117 (corrected m.p.) or above that temperature, then 

 the addition of vegetable fat may be said to be proved. 



When using this method the melting point must always be 

 corrected, which may be done with sufficient accuracy from the 

 following formula : 



M = T+n(T-t), 0-000154. 



M = the corrected melting point. 

 T = the observed melting point. 

 n = the length of the column of mercury, expressed in degrees 



of temperature, above the level of the liquid. 

 t = the temperature of the air surrounding the column of 



mercury above the level of the liquid. 



Siegfeld l has shown that by means of this method an adul- 

 teration with 10 per cent, margarine or cocoa butter can be 

 proved with certainty if 50 g. of the butter are used. 



The phytosterine acetate test is certainly somewhat tedious 

 to carry out, but when properly done it gives absolutely incon- 

 trovertible results, for it is based on the fact that pure butter- 

 fat only contains cholesterine and never phytosterine. Also 

 the melting point of phytosterine acetate is considerably higher 

 than cholesterine acetate, so that a small admixture of phyto- 

 sterine must make itself apparent by a rise in the melting 

 point. 



In making the test 100 g. of fat can of course be used, and this 

 is more convenient, but with practice 50 g. will be found to be 

 quite sufficient. 



6. The Latent Colouring of Margarine. 



On account of the difficulty in detecting the addition of 

 margarine to butter, either by chemical or physical tests, it 

 has been decreed in certain countries, e.g., Germany, Austria, 

 Belgium, Denmark, Sweden, and France, that in the manu- 

 facture of margarine some easily recognisable material must be 

 added. By means of a simple chemical test it is then easy to 

 prove the presence of margarine in butter. 



1 Zeitftchrift fur Untersuchiing der Nahr.- und GemiMmiftel, 1904, No. 10, 



p. 577. 



