910 



SCIENCE. 



[N. S. Vol. XXIII. No. 598. 



kind of tobacco which were originally in 

 fair condition were placed in each desicca- 

 tor. After eighteen days the samples were 

 again weighed, and the condition of the 

 tobacco was carefully examined. The 

 tables give the results of these experi- 

 ments. 



•*: 4 



L05 1.10 1.15 I.a0 1.25 



Density of H SO Solutions 



Fig. 2. Showing the loss or gain in weight in 

 various cigar tobaccos. 



From the above tables and Fig. 2 it will 

 be seen that the filer and wrapper tobaccos 

 are brought to a good physical condition 

 by acquiring the same vapor pressure as a 

 sulphuric acid solution of density about 

 1.18. The hinder tobacco requires a some- 

 what weaker solution, 1.12. From the 

 tables of Richards* for the vapor pressure 

 of sulphuric acid solutions at 20°, the 

 vapor pressure of a solution of density 1.16 

 is 15 mm. and of a solution of density 1.31 

 is 10 mm. A solution of sulphuric acid 

 of density 1.18 has a vapor pressure of 

 about 14 mm., while a solution of density 

 1.12 has a vapor pressure of about 16 mm. 

 A solution of density 1.16 would probably 

 keep all three kinds of tobacco in good 



* hoc. cit. 



condition. Lescoeur's results^ have been 

 consulted to find saturated solutions which 

 yield vapor pressures at 20° in the neigh- 

 borhood of 15 mm. The following table 

 gives these figures. 



Table VI. 



Vapor pressure of saturated solutions of various 



salts at 20°. 



Of the above salts, zinc and copper sul- 

 phate are ruled out on account of their 

 toxic action, if by any accident the salt 

 should come in contact with the tobacco. 

 Sodium sulphate has a rather high vapor 

 pressure and is, therefore, best suited for 

 the binder tobacco, while potassium sul- 

 phate with a vapor pressure below 15 mm. 

 is best suited for filler and wrapper 

 tobaccos. The best salts for all three are 

 probably ammonium sulphate and potas- 

 sium nitrate. Saturated solutions of am- 

 monium sulphate have been used in the 

 box which has been described and samples 

 of the three cigar tobaccos which were very 

 dry were placed on the shelves. At the 

 end of ten days these tobaccos were pro- 

 nounced by Mr. McNess, of this Bureau, to 

 be in prime condition. 



Thus, to bring cigar tobaccos into a 

 proper condition of moisture preparatory 

 to manitfacture it is svtfficient to place 

 these tobaccos in a confined space in which 

 there is exposed a large surface of a satu- 

 rated solution of ammonimn sulphate or 

 potassium nitrate. After the cigars have 

 been made up, they may be brought to a 

 proper condition of moisture for consump- 



