10 BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE. 



Kissling. The pure ash, the carbohydrates, including starch, reducing 

 sugars, pentosans, and crude fiber, and the several nitrogenous con- 

 stituents were determined by the following methods: 



Pure ash. — The tobacco was incinerated in the usual manner in a 

 platinum dish with a cover, care being taken to avoid fusing the ash. 

 The pure ash is obtained by correcting for carbon dioxid, carbon, and 

 sand. 



Starch. — Rather than attempt to determine starch directly by the 

 diastase method it was preferred to obtain the total of the carbo- 

 hydrates hydrolyzed by hydrochloric acid, using the official method, 

 and to dete rmin e also the pentosans. It is thought that for purely 

 comparative results this method is satisfactory, and nearly all pre- 

 vious analyses of tobacco for starch which the writers have seen have 

 been based on this method of the direct hydrolysis with acid, but 

 usually without determining the pentosans. 



Pentosans. — The determinations were made by the official method, 

 the phloroglucin being calculated to pentosan by Krober's tables. 



Reducing sugars. — Since nicotine, even in a moderately concen- 

 trated solution, exerts a reducing action on Fehling's solution, it is 

 removed before preparing the solution for the determination of reduc- 

 ing sugars. This is done by moistening 5 grams of the tobacco with 

 5 c. c. of a 5 per cent solution of caustic potash in absolute alcohol 

 and digesting the mixture in a flask with 100 c. c. of absolute ether. 

 The reducing sugar is then extracted with 60 per cent alcohol, the 

 alcohol removed by evaporation, the water solution made up to vol- 

 ume, clarified with normal lead acetate, and the sugar determined as 

 glucose by the Allihn method. 



Crude filer. — The official method, as modified by Sweeney and by 

 Kennedy, was employed. 



Nonvolatile organic acids. — The method of Kissling 1 was followed 

 for the determination of oxalic, citric, and mafic acids. We have 

 found it necessary, however, to increase by at least 25 per cent the 

 quantity of sulphuric acid recommended by Kissling to be added to 

 the tobacco, to insure the liberation of all the organic acids. This 

 was particularly true of the cured samples, from which only very 

 small portions of the oxalic acid could be extracted when only 10 

 grams of a 20 per cent sulphuric-acid solution were added to 10 grams 

 of the tobacco. 



Protein nitrogen. — Tests having shown that the method of Mohr 2 

 gives excellent results for the purpose in view, it was followed in 

 preference to the official (Stutzer) method. In this process the 

 tobacco is simply boiled with a dilute acetic-acid solution, filtered 



1 Kissling, Richard. Beitrage zur Chemie des Tabaks. Zur Tabakanalyse. Chemiker-Zeitung, Jahrg. 

 28, No. 66, p. 775-776, 1904. 



1 Mohr, E. C. J. Gepfliickter und am Stamme getrockneter Tabak. Die Landwirtschaftlichen Ver- 

 Suchs-StatioDen, Bd. 59, p. 274, 1903. 



