112 PUBLIC HEALTH CHEMISTRY 



MUSTARD. 



Mustard is the seed of Sinapis alba and S. nigra. It is 

 commonly sold as a powder. Pure mustard contains 14 

 per cent of carbohydrates, o-66 per cent of volatile oil, 35 

 per cent of fixed oil. The chief adulterations are : the 

 addition of starch, bringing up the percentage of carbo- 

 hydrates to 67 per cent ; the abstraction of oil, reducing 

 it to as low as 7 per cent ; the addition of turmeric to 

 colour, and cayenne pepper to make the taste sharper. 

 Examine with microscope for hexagonal cells in white 

 mustard. 



PEPPER. 



Black pepper is derived from Piper nigrum. White 

 pepper is made from the inside of the berry. 



Moisture, 9 to 11 per cent ; ash, 2 to 5 per cent ; ash 

 insoluble in HC1, under 1 per cent for white, under 2 per 

 cent for black pepper ; fibre, 4 to 6 per cent in white, 8 to 

 11 per cent in black ; carbohydrate, 65 per cent in white, 

 50 per cent in black ; piperin and fixed oil, 8-2 per cent 

 in white, 7-8 per cent in black. Adulterations : linseed, 

 mustard husks, wheat and pea flour, rape cake, ground 

 rice, ground olive stones (poivrette), sweepings. 



GINGER. 



Ash, under 3-9 per cent ; soluble ash, over 1-7 per cent ; 

 cold water extract, over 8-7 per cent. 



PEAS. 



Test peas, especially when tinned or bottled, for copper, 

 used in " greening " them. 



Qualitative Test. Acidify with HC1 and put a piece of 

 bright steel in the liquid in which the peas are immersed. 

 Stand all night. Deposit of copper, of a coppery colour. 



Quantitative Test. Ash 20 grm. of peas, boil ash with 

 dilute sulphuric acid. Filter, and make up filtrate to 

 50 c.c. Test amount of copper colorimetrically, or 

 gravimetrically. 



MEAT EXTRACTS AND ESSENCES. 



Total nitrogen, by Kjeldahl ; protein, N x 6-25 ; moisture ; 

 ash ; reaction ; carbohydrate ; fat ; antiseptics ; poisonous 

 metals. 



