SPECTROSCOPIC DETERMINATION OF LITHIUM. 25 



of wire suggested b}- Truchot by which a fairly uniform drop (-»f 

 Hquid is picked up each time is an improvement. 



In Table I ' are given some results showing the relative accuracy 

 of readings made under strictly uniform conditions, using a straight 

 wire and Bunsen lamp. Results are given on standards of known 

 amounts of lithium chlorid without the addition of sodium chlorid, 

 with varying amounts of lithium chlorid plus 10 mg of sodium chlorid 

 per cubic centimeter, and with varymg amounts of lithium chlorid 

 plus 100 mg of sodium chlorid per cubic centimeter. The masking 

 due to potassium was tested and found to be very much less than 

 that duo to sodium; therefore, in view of the small amoimts of 

 potassium usually found m mineral waters as compared with sodium, 

 the effect of potassium w^as not studied further. 



In order to avoid the personal equation as nmch as possible, the 

 solutions w^ere prepared by an assistant and read bj^ two persons unac- 

 quainted with the value of the solutions, one analyst making tw^o 

 sets of observations but on different days. A preliminary test of 

 the unknown solution at once showed whether the standards to be 

 used for comparison should be the set containmg 10 mg of sodium 

 chlorid per cubic centimeter or that contaming 100 mg of sodium 

 clilorid per cubic centimeter. The appropriate set of standards for 

 comparison w^as then selected. These standards were prepared in 

 sets containing amounts of lithium varying from 0.01 to 1.00 mg per 

 cubic centimeter, and the comparisons made in a manner suggested 

 by the comparison of colorimetric standards. 



1 Skinner, "A spectroscopic method for the determination of lithium," a paper read at the meeting of 

 American Association for the Advancement of Science, 1908. 



