196 



FOODS AND FOOD ADULTERANTS. 



microscopically. The structure is that characteristic of the hard thick- 

 ened schlereucbyma or stone cells, polyhedral and elongated in shape 

 with thickened walls and little filiform canals. They are most readily 

 made out with polarized light, toward which they are optically active, 

 while the remaining particles of pepper or pepper husks are not seen in 

 the dark field, being inactive. 



Of this adulterant H. Rabourdin has made some investigations, pub- 

 lishing his results in an interesting paper,* giving a general account of 

 the various peppers of commerce and the use of olive stones as an 

 adulterant, as well as other materials already mentioned. He finds no 

 difficulty in recognizing the falsification owing to the presence of the 

 numerous sclerenchyma or stone cells, which are distinguished readily 

 with polarized light, but the quantitative determination is more difficult. 

 This, however, he affirms, can be accomplished by determining the resi- 

 due left on boiling the suspected sample for one hour with 1 per cent, 

 sulphuric acid after thorough washing with water. In the course of 

 the operation the presence of the olive stones is apparent from their 

 clinging in the form of a reddish powder to the walls of the flask or 

 beaker in which the digestion has taken place, and separating more or 

 less from the pepper hulls on account of their different specific gravity. 



For pure peppers the following percentage of residue was found : 



On the other hand olive stones were found to contain; 



From these figures the following factors are derived 



*J. do Pharni. ct dc Chioiie, [5], 9, 289-297. 



