232 Proceedings of the Royal Society of Edinburgh. [Sess. 
Estimation of the Total Chlorine. 
The amount of combined chlorine per litre of each sample was found 
by the usual method, in which a given volume of the water is titrated by 
standard silver nitrate, with potassium chromate as the indicator. 
The necessary measuring instruments consisted of a 10 c.c. pipette* 
furnished with a tap and fine point, and with fiducial marks above and 
below the bulb, and a 50 c.c. burette which could be read direct to 0T c.c. ; 
the burette was standardised at the Reichsanstalt, Charlottenburg, and the 
pipette subsequently compared with it. 
The silver nitrate was supplied by Messrs Johnston, Matthey & Com- 
pany, and was labelled “ triple crystallised.” The crystals were reduced to 
a powder and then dried in a water oven at a temperature of 95°-98° C. 
A standard solution was then prepared by weighing the salt direct, dis- 
solving in water, and diluting to an appropriate volume. This solution 
was then compared with (1) a solution of highly purified sodium 
chloride, and (2) a standard sea- water received from Dr Nansen; the latter 
standard had been used by me in connection with the analyses of waters 
brought home in 1904 by the Antarctic Expedition. The chlorine values 
obtained for the silver nitrate by these methods did not differ by more 
than 1 in 600, and their mean value was accepted as the true one. 
In making a determination of the combined chlorine, the water was 
first drawn into the burette direct from the bottle containing the sample ; 
about 9*7 c.c. of it was then allowed to run into a porcelain dish and 
approximately titrated with the silver nitrate solution ; the remaining 
portion was then delivered into the dish and the titration completed. By 
this method of procedure a very complete and uniform draining both of 
burette and pipette was in every case secured. 
The results obtained are set forth in Tables Y. and VI. on pp. 219 
and 223. 
* For the continued loan of this pipette, I have to thank Dr Dickson. 
{Issued separately September 11, 1907.) 
