Chemical Examination of Waters. 153 



but a much larger proportion may be present without affecting 

 the sense of taste. 



Action on Lead. — As lead is still used to a considerable 

 extent in the distribution and storage of water, it is of conse- 

 quence that the water adopted for the supply of Sydney should 

 have no undue action on the metal. In a certain number of the 

 waters submitted for examination, the amount of action was 

 determined in the following manner : — A piece of sheet lead, 

 exposing 20 square inches of surface, was immersed in a pint of 

 each specimen, and allowed to stand twenty -four hours ; the 

 proportion of lead dissolved in the water was then determined. 

 Examined in this way, different specimens of Sydney water, 

 drawn at different times and places, were found to acquire a pro- 

 portion of lead varying from one-tenth to one-fifth of a grain per 

 gallon. The worst water examined was that of the Woolli 

 Creek, which took up about one grain per galloa. The Woro- 

 nora took up about one-tenth, and the Cataract the same. The 

 "Warragamba and the Nepean at Penrith had about the same 

 action, each taking one-twelfth. Water from Pheasant's Nest 

 took one-eighteenth ; George's River, above Liverpool dam, one- 

 thirtieth ; and the Grose a mere trace. With the exception, 

 then, of "Wolli Creek, the Sydney water was the worst of the 

 running streams examined ; which is so far satisfactory, because 

 we already know that Sydney water may be conveyed through a 

 moderate length of lead piping without dissolving so much of the 

 metal as to be injurious. Lead cisterns even may be used with 

 impunity for storing the Sydney water, provided they be well 

 painted. White zinc paint seems well adapted for this purpose. 

 And water that has been contaminated with lead in any way may 

 be effectually purified by filtration through sand. 



The above experiments illustrate the fallacy of the oft-repeated 

 assertion that in contact with lead a water is dangerous in pro- 

 portion to its purity. The Grose was one of. the purest rivers 

 examined, and it had scarcely any action on lead. The Woolli 

 Creek with 20 grs. of solid matter per gallon, had the most 

 action, and water from a standing pool at head of Prospect Creek, 

 with 24 grs. of solid matter, came next in order, having taken up 

 one-third of a grain of lead in 24 hours. On the other hand 

 George's River, with 26 grs. of dissolved matter, took up 1-30 

 a grain of lead, the same as the Tan Yean, with only 8 grs. of 

 dissolved matter. In short, no connection can be traced between 

 the amount of action on lead. 



Professor Prankland has recently suggested that many waters 

 are prevented from acting on lead by the presence of phosphate 

 of lime. I have not determined the phosphates quantitatively in 

 any of the above waters, but at present I am under the impres- 

 sion that the great differences in the action of these waters 



