178 



FOODS AND FOOD ADULTERANTS. 



METHOD OF LEEDS AND EVERHART. 



Moisture and ash are determined as usual; oil, in a portion of mus- 

 tard dried at 105, by ether in an extraction apparatus, with subse- 

 quent drying at 100. From the dried residue the sulphocyanide of sin- 

 apin and the myronate of potassium are extracted in a similar way by 50 

 per cent, alcohol. The extract is dried, weighed, and ignited, and from 

 the sulphate of potash in the ash the myronate is reckoned and the 

 sulphocyauide obtained by difference. The residue, containing myrosin, 

 and cellulose and a little coloring matter, is freed from alcohol and treated 

 with one-half per cent, sodic hydrate solution. The washed residue is 

 weighed and ignited for cellulose. The filtrate containing all the 

 inyrosin is nearly neutralized with dilute hydrochloric acid, 50 c. c. of 

 Bitthausen's copper sulphate solution added, and then dilute sodic hy- 

 drate to near neutrality. The heavy green myrosin copper compound 

 is filtered off, dried at 110 C., weighed, and ignited. The difference is 

 the myrosin. 



Analyses carried out after this method in triplicate are as follows : 



The amounts of nitrogen and sulphur in this mustard were : 



Nitrogen 5.337 



Sulphur 1.489 



Calculated from these figures according to the method of Hassall 

 would be found the following : 



Myronate of potassium 61 



Sulphocyanide of sinapine 10.71 



Myrosin 28.52 



Showing a close agreement with the direct determinations. 



Direct methods are, however, usually preferable and this would, no 

 doubt, be a good one were it not that dilute alcohol in the case of ad- 

 mixture of flour would dissolve so much of the albuminoid matter and 

 ash of the latter as to invalidate the determination of myronate. It is 

 therefore open to criticism. 



E. Waller and E. W. Martin * in 1882 made an examination of mus- 

 tards manufactured and sold in New York City, attention being paid 

 to moisture, oil, and soluble and insoluble ash. They also examined 

 mustard pastes, and compared their results with some pure mustards 

 from the English market. Their analyses are as follows : 



* Analyst 9, 166-170. 



