26 



THE DETERMINATION OF LITHIUM. 



Table 1.— Determination of lithium hy modified method of Truchot. 



WITH NO SODIUM CHLORID. 



WITH 10 MG SODIUM CHLORID PER CUBIC CENTIMETER. 



WITH 100 MG SODIUM CHLORID PER CUBIC CENTIMETER. 



Ballmann^ diluted a solution containing a known amount of lithium 

 until the lithium line could not be seen in the spectroscope, and then 

 diluted the unlaiown solution to the point where the line could not be 

 seen. By considering the concentration of lithium the same in both 

 cases he was able to calculate the amount in the unknown solution. 

 In his experiments the litliium line was seen easily with a volume of 

 1,320 cc, seen faintly twice and missed once when the volume was 

 1,340 cc, and with a volume of 1,360 cc could not be seen at all. This 

 would appear to make the error of the method about 2 per cent. The 

 lithium line could not be seen when 1 mg of lithium chlorid was made 

 up to 3,345 cc (0.0003 mg in 1 cc). Ballmann used a spiral loop 2.5 

 mm in diameter and 3.5 mm along the axis. 



Jones,^ in a note concerning the work of Ballmann, described some 

 of his own experiments on quantitative spectroscopic determinations. 

 He diluted solutions until a measured volume, usually 0.3 cc, intro- 

 duced into the flame failed to give the Imes in the spectroscope. He 

 used pellets of cotton or filter paper folded as for burning. The 

 solution was absorbed by the porous material and after drymg and 

 burning off the combustible matter the ash which was left in a porous 



1 Zts. anal. Chem., 1875, U,: 297. 



2 Chem. News, 1876, 34: 122. 



