SPICES. 59 



15. DETERMINATION OF NITROGEN. 



(a) KJELDAHL METHOD. 



( For all spices except black and white pepper. ) 

 See methods of the Association of Official Agricultural Chemists. a 



(b) GUNNING-ARNOLD METHOD. 



( For black and white pepper. ) 



Owing to the presence of piperine, the Gunning- Arnold method b must be used to 

 determine nitrogen in both black and white pepper. Mix 1 gram of the material 

 in a 600-cc Jena flask with 1 gram of copper sulphate, l.gram of mercuric oxid, 15 

 to 18 grams of potassium sulphate, and 25 cc of sulphuric acid. After heating gently 

 until frothing ceases, boil the mixture from two to four hours. When nearly cool, 

 add about 300 cc of water, 50 cc of potassium sulphid solution (40:1,000), and 

 sodium hydroxid solution to alkaline reaction. Distill into standard acid and titrate 

 with standard alkali, as usual. 



16. DETERMINATION OF NITROGEN IN NON- VOLATILE ETHER EXTRACT. 

 WINTON, OGDEN, AND MITCHELL METHOD. 



(For black <utd irliite pepper. ) 



Exract 10 grams of pepper for twenty hours in a continuous extraction apparatus 

 with absolute ether, collecting the extract in a weighed Jena flask of about 250-cc 

 capacity. Evaporate the ether, dry first at 100 C., and finally to constant weight at 

 110 C. Determine the nitrogen in the weighed extract by the Gunning- A mold 

 method, digesting in the same flask used for the extraction. Calculate the parts of 

 nitrogen in 100 parts of the non-volatile ether extract. 



Results on authenticated samples show that 100 parts of non-volatile ether extract 

 from black pepper, owing to the presence of piperin, contain not less than 3.25 

 parts, and from white pepper not less than 4.00 parts of nitrogen. Linseed meal 

 and other oily adulterants may contain about the same amount of ether extract as 

 pepper, but this extract is practically free from nitrogen. 



If desired, crude piperine may be calculated from the nitrogen by multiplying by 



17. DETERMINATION OF COLD WATER EXTRACT. 

 (For ginger. ) 



Place 4 grams of ginger in a graduated 200-cc flask, add water to the mark, shake 

 at half-hour intervals during 8 hours and let stand 16 additional hours, without 

 shaking. Filter and evaporate 50 cc to dryness in a flat-bottomed metal dish. Dry 

 to constant weight at 100 C. 



Cold water extract was first determined by Allen and Moor d as a means of detect- 

 ing exhausted ginger. The process of Winton, Ogden, and Mitchell e here described 

 is more easily carried out and gives more concordant and somewhat higher results 

 than extraction on a filter with the same volume of water added in consecutive por- 

 tions. Complete extraction on a filter was found im practicable. 



U. S. Dept. of Agr., Div. of Chem., Bui. 46 revised, p. 14. 



' Ztsclir. jinal. Clu-in. 1,v.'J, SI, 525; Conn. Agr. Expt. Sta. Kept.. 1898, p. 190. 



"See Appendix, p. 165. 



i Analyst, 1894, 1, rji. 



Conn. Agr. Expt. Sta., Kepi, is-.is, p. 190. 



