CHEMICAL ANALYSIS 41 



day being 1*5 litres, and the average water-supply 150 litres, or 

 33 gallons per head per day. 



Sulphates as SO3 in Parts per 100,000. 



Urine ... ... ... ... ... ... 160 



" Typical sewage " ... ... ... ... i-6 



London waters : 



West Middlesex 2*46 



Kent 5'4 



New River ... ... ... .. ... i'33 



Loch Katrine (Glasgow) water 0-47 



Phosphates. — Both urine and faeces contain, in proportion to 

 the solid matter, a large quantity of phosphates both of the 

 alkahes and of lime and magnesia ; hence, in testing drinking- 

 waters for sewage contamination the phosphate test is of great 

 value. But in examining sewage effluents both from coke filters 

 and from chemical treatment, I have found that the phosphates 

 have sometimes almost entirely disappeared, owing to the fact 

 that they are precipitated by iron present in the materials, or 

 by lime in the water or precipitants, or that they are absorbed 

 by various organisms. Therefore in this case the determina- 

 tion is of less value. 



Potassium and Sodium. — 

 In urine 



/Na ... o'4 per cent. 



IK ... 0-8 



In faeces More K than Na. 



Porter found in the ash of human excrement 6'i per cent, of 

 KgO and 5*07 per cent, of NagO.^ 



Therefore, the ratio of the alkalies sometimes furnishes in- 

 formation as to the character, whether faecal or urinous. It 

 must be remembered, however, that the urine of horses and 

 cattle contains a considerable amount of potassium. 



From a large number of analyses of London sewage by 

 Letheby, Fuller calculates the amount of phosphoric acid and 

 potash discharged in the sewage per head of population per day 

 to be in grammes : '^ 



^ Ann. Chem. PJiarm., Ixxxi., 109. 



■^ American Technology Quarterly^ XVI., ii., 1903, p. 138 ; Letheby, " The Sewage 

 Question," Bailliere, Tindall and Cox, 1872, p. 137. 



