II July. 1910.] The Punjication of Muddy VJaters. 439 



takes rather more of it to be effective. The sahs of monovalent m.etals, 

 such as sodium and potassium, are of no use. 



An interesting observation which was made was the power of acid to 

 reduce the quantity of chloride of iron, otherwise necessary to clear a given 

 volume of water. 



It was found that \ lb. of ferric chloride + \ lb. of 30% hydro- 

 chloric acid was as effective in its action as i lb. of ferric chloride by 

 itself. 



Acid has a similar beneficial effect upon the action of alum, though 

 the degree of improvement is not so marked. 



The Geological Factor. — As the precipitation of the mud from any 

 water by the addition of a chemical is a physical process rather than a 

 -chemical one, the method is of wide use; and can be applied to waters of 

 different geological regions. 



Samples of water have been collected from districts representing many 

 of the chief geological formations of Victoria, and in every case the 

 chloride of iron acted rapidly and well. Alum was not tried in every case, 

 but may be definitely assumed to act well also. 



The samples were obtained in March, when the water dams were 

 nearly dry and the water at its worst. Here are some of the results: — 



Cranbourne. — Water polluted by cattle ; growth of weeds. i lb. iron chloride 

 per 1,000 gals. 



River at Dandenong. — Dirty water. ^ lb. iron chloride cL^ared i,ooo g.als. 

 Excellent bacterial purity of clear water. 



Cemetery. — Water fair. 5 lb. iron chloride per i,ooo gals, immediately cleared 

 it (15 min.). 



Two Milei. N. of C am f bell field. — Very dirty water j cattle. i lb. iron chloriile 

 per 1,000 gals. 



Campbell field. — Water fair; from clav i>its. 5 lb. per 1,000 gals, quickly 

 successful. 



Temflestowe. — Water witli thick red mud. i lb. ]>cr 1,000 gals, cleared 

 splendidly. 



Warrandyte. — Typical niuddv water. ^ lb. per 1,000 gals. 



These waters are from country whose geological nature comprises the 

 Tertiary formations, occurring in patches in Southern Gippsland {e.g., 

 Oranbourne) ; the Silurian formations, which are very extensive and cover 

 Anglesey, with the western half of Wonnangatta ; and the Neiver Basalt 

 of the great Western districts. 



Not examined as yet are waters from the Ordovician, the gold-bearing 

 country of Bendigo, Ballarat, or the Bacchus Marsh region ; the Jurassic 

 of Southern Gippsland ; and the Receipt formations of the north and north- 

 ^vest. There is no reason why these waters should not behave as uniformly 

 as those already examined. 



The Selection of a Chemical Precipitant. — From what has been 

 shortly stated in the previous paragraph, the ideal substance w^ould be a 

 cheap salt of aluminium, iron, or chromium. From the practical point 

 of view, the cheapness is almost as important as the chemical-efficiency, 

 and consequently for actual u.se only the following need be named, viz., 

 alum, chloride of iron, lime. 



The last of these is able to compete only on account of its cheapness. 

 It is especially to be noted that it is not nearly so " brilliant " in its 

 action as either alum or chloride of iron. It is. however, a practical 

 .substance to use. 



