288 Gooch and Brooks — Rapid method for the 



acid acting. It often happens, when the temperature of the 

 liquid in the test-tube rises a little higher than need be, that 

 fumes of sulphuric acid pass into the bulbs to such an extent 

 as to produce a white precipitate of lead sulphate when the 

 lead acetate is subsequently added. In such cases the lead sul- 

 phate is easily dissolved by the addition of a little amnionic 

 acetate in saturated solution, and gentle heating, and, on cool- 

 ing, the yellow chromate is either precipitated or simply colors 

 the liquid. It is advisable, however, as our experience proved, 

 not to employ more of the amnionic acetate than the occasion 

 requires, as it undoubtedly exerts some solvent action upon the 

 lead chromate as well as upon the sulphate. 



AYe proceeded to test in the manner described the applica- 

 bility of this process by first testing the action upon solutions 

 of pure potassium chloride. 



KCl taken. 



Final volume. 



Reaction obtained. 



0-0030 



rjcm3 



Marked precipitation. 



0-0020 



5 



Marked precipitation. 



o-ooio 



5 



Distinct precipitation. 



0-0005 



5 



Distinct color. 



0-0004 



5 



Faint color. 



0-0003 



5 



Faint color. 



0-0002 



5 



Faintest color. 



o-oooi 



5 



Doubtful. 



o-oooi 



5 



None. 



o-oooi 



5 



None. 



It appears, therefore, that the chlorine in 0'0005 grm. of potas- 

 sium chloride is found certainly, and that indications of chlo- 

 rine in amounts of the chloride ranging as low as 0*0002 grm. 

 are fairly evident in tests made upon the pure substance taken 

 in solution, evaporated, and treated as described. 



The effect of submitting the solution of the chloride contain- 

 ing also a known amount of potassium iodide to the process 

 previously described for liberating the iodine, of then neutral- 

 izing the solution with sodium carbonate, evaporating to dryness, 

 and treating with sulphuric acid and potassium di chromate, is 

 shown in the following record. The potassium iodide used in 

 these tests was prepared free from chlorine by the action of 

 resublimed iodine upon iron wire and subsequent treatment 

 with pure potassium carbonate. The nitrite was freed from 

 chlorine by adding to its solution a little silver nitrate, faintly 

 acidulating with nitric acid, and filtering off the chloride pre- 

 cipitated with a small amount of the nitrite. 



KI taken. 



KCl taken. 



Final volume. 



Reaction obtained. 



O'l grm. 



0-0020 



grm. 



5 



cm. 3 



Distinct precipitation. 



o-i 



o-ooio 





5 





Distinct color. 



o-i 



0-0005 





5 





Faint color. 



o-i 



0-0004 





5 





Faint color 



o-i 



0-0003 





5 





Faintest color. 



o-i 



0-0002 





5 





Faintest color. 



o-i 



o-oooi 





5 





None. 



