360 THE ISOCHLORS OF NOVA SCOTIA. VICKERY. 



nitrate solution used in titrating 100 cc. sample of water 

 multiplied by ten will give the number of parts of chlorine 

 per million parts of water in the sample. 



The indicator solution was prepared by weighing two 

 grams of chemically pure potassium chromate dissolved in 

 100 cubic centimeters of water and adding silver nitrate 

 until a permanent red precipitate is formed — the filtrate 

 would thus be chloride free. One or two cubic centimeters 

 of this indicator solution were used, depending upon the 

 color of the water under examination. 



The experimental method used in determining the chlorine 

 content of a sample of water was to measure 100 cc. of water 

 into a procelain casserole and color it with one cubic centi- 

 meter of the indicator solution. This was then titrated until 

 a faint difference in color was observed between the sample 

 and another one similarly prepared, which was placed beside 

 it. By this means a very sharp endpoint was easily attained. 

 The 100 cc. graduate was used in measuring the samples, 

 as it was found impracticable to carry a 100 cc. pipette. In 

 some cases difficulty was experienced in getting a sharp 

 endpoint,- owing to the water being discolored by peat, but 

 by the use of the clouded control only in two or three instances 

 was the error greater than .03 cc. of solution, that is, .3 parts 

 per million. 



The work of obtaining the samples of water necessitated 

 covering large stretches of country; the work was of necessity 

 done slowly, at different seasons of the year, and under dif- 

 ferent conditions of drought and freshet, making strict com- 

 parisons between the results obtained difficult. With a 

 few exceptions the samples were collected by the writer, 

 with the observance of every precaution, and all the analyt- 

 ical work was carried out by him. No use could be made 

 of data derived from Governmental Reports, since water 

 analyzed in public laboratories would probably be taken 

 from doubtful or suspected sources. Tlio work was done 



