134 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



sodium chloride in a known volume of distilled water. 

 The sodium chloride was obtained from the ordinary 

 crude salt by precipitation from a strong aqueous 

 solution by means of hydrochloric acid. The precipi- 

 tate was filtered, dried, and finally fused. The actual 

 strength of the salt solution prepared was nearly ■^ Si 

 and this could then be diluted as required. 



The ammonium sulphocyanide solution was prepared 

 by dissolving the pure salt in water in such proportions 

 as to make it approximately decinormal. Its actual 

 strength was not determined as it was titrated against 

 the silver nitrate solution only to find the ratio between 

 their strengths. 



Saturated solutions of the two indicators — potassium 

 chromate and iron alum — were employed, one drop 

 being sufficient for each titration. 



(b.) — Volhard's Method. 



A sample of sea water (about 10'0 cc.) was titrated 

 as a preliminary, in order to find about the amount of 

 silver solution required. 



The accurate determinations were then done in the 

 following way : — 



lOcc. of the sea water was measured from a pipette 

 into a beaker, and mixed with a little distilled water. 

 About 2cc. more silver solution was then added than 

 the preliminary examination had shown to be neces- 

 sary. The mixture was thoroughly shaken and allowed 

 to settle, and the nearly clear supernatent liquid was 

 filtered. The residue in the beaker was twice washed 

 with distilled water, and the washings were mixed with 

 the filtrate after they themselves had also been filtered. 

 All the excess of silver was now found to be in the 



