A COMPLETE ANALYSIS OF SYDNEY WATER. 151 



centrated and the metals of the zinc group precipitated as 

 sulphides. Manganese was separated by precipitation as 

 dioxide with bromine water, and weighed as Mn 3 4 , and 

 the zinc was precipitated as carbonate and weighed as 

 oxide. As the amount of zinc was rather high, a week 

 was allowed to elapse, and the zinc re-estimated in a further 

 50 litres of water, the previous result being confirmed. 

 Neither nickel nor cobalt was present. 



Total gases— These were determined by boiling a known 

 volume of water under reduced pressure and measuring 

 the amount of gas given off, allowance being made for 

 temperature and pressure. 



Pree oxygen— Two methods were used for the estimation 

 of the oxygen, viz. ThreshV and Winkler's, 2 but in neither 

 case did the water show a saturation of more than 60°/°. 

 This is no doubt due to the action of the iron pipes on the 

 oxygen in the water, which partially removes the oxygen 

 forming oxide of iron. 



Free carbonic acid— To one litre of the water was added 

 a little phenol-phthalein solution and the free carbonic acid 

 determined by running in N/50 sodium carbonate until a 

 faint permanent pink colour was produced. 



Nitrogen— This was found by subtracting the amounts of 

 the free oxygen and carbonic acid from that of the total 



Analysis of the Total Solid Residue. 

 Silica, Iron, Aluminium, Calcium and Magnesium— Four 

 litres of the water were taken for the estimation of the 

 total amounts of these constituents. The total solid 

 residue was ignited and the silica removed in the customary 

 manner and weighed. The iron and aluminium were pre- 



1 Journ. Chem. Soc, 1890, p. 185. 2 Berichte 21, (1888) 2843. 



