SEA-FISHERIES LABORATORY. 133 



- 4. — Suspended Matter. 



This was not estimated owing to the difficulty of filtering 

 large volumes of water, and of weighing small amounts of 

 ash. It was very abundant in the Mersey water at low 

 tide, but not nearly so abundant at high tide. There 

 was quite an appreciable amount of suspended material 

 in all samples off the Lancashire coast, but in the open 

 sea, and round the Isle of Man, the water is practically 

 clear. 



For the determination of the specific gravity and other 

 characters, the sediment was allowed to settle and the 

 clear water decanted off. 



5. — Estimation of the Chlorine. 



This was done with the greatest possible accuracy, both 

 by Yolhard's method and also by titration with standard 

 silver nitrate solution, using potassium chromate as 

 indicator. 



The exact process by each method is given and also the 

 results, for the sake of comparison. 



(a.) — Preparation of Solutions. 



The silver nitrate solution was prepared by 

 dissolving the pure fused salt in sufficient water to 

 make about a decinormal solution. This could then 

 be diluted to any desired extent. 



It was standardised by titration against the sodium 

 chloride solution (which see), using potassium 

 chromate as indicator, and also by Volhard's method 

 It was restandardised about once a week, in order to be 

 certain as to its exact strength from time to time. 



The sodium chloride solution was prepared by dis- 

 solving an accurately determined weight of pure, dry 



