152 Chemical Examination of Waters. 



being George's River at Liverpool, Nepean at Blaxland's Mill, 

 South Creek, and the Woronora, all of which contained earthy 

 chlorides in notable proportion. The water from the Mulwarree 

 ponds is remarkable for containing more sodium than the chlorine 

 present can take up. 



The question may occur to what extent may any of the usual 

 impurities be present in water without ill effects, whether in do- 

 mestic use or in manufactures. To this question no definite 

 answer has, so far as I know, been attempted ; but we may arrive 

 at some useful conclustions. First, in regard to organic matter, 

 we may safely say the less of it the better ; but still if it be en- 

 tirely of vegetable origin I do not think that any harm is likely 

 to arise from as much as two grains to the gallon. If, however, 

 it be partly of animal origin it is considered to be more dangerous, 

 and I would not venture to assign in this case the limits of safety. 

 It is unfortunate that there is at present no chemical operation 

 known by which the exact amount of organic matter in water can 

 be determined, or by which the animal matter can be separated 

 from the vegetable. If we find the organic matter to be much 

 azotised, if animalcules breed readily, and if there be ammonia 

 or nitrates present, we may reasonably suspect that the water 

 has been contaminated with animal matter, and shun it accord- 

 ingly. 



With regard to saline matter, I should say that common salt 

 may exist to the extent of 10 grains per gallon without harm, 

 and if a portion of this be replaced by other neutral compounds 

 of sodium or potassium there still need be no apprehension. I 

 believe that it takes about 20 grains of common salt per gallon 

 to communicate any marked taste. 



Carbonates of lime and magnesia may exist to a large extent in 

 water without affecting the taste or being in any way injurious 

 to health. There are waters near London with as much as 18 

 grains of chalk per gallon, and yet are much esteemed. As to 

 the effects of the sulphates and chlorides of these bases, I am 

 more uncertain. Probably a few grains per gallon, not more than 

 4 or 5, would do no harm. But for cooking and cleansing and 

 manufacturing purposes these hard waters are very unsuitable ; 

 anything above 5 degrees of hardness should, if possible, be 

 avoided. 



As to iron in water, there is too much as soon as it becomes 

 sensible to the taste ; and, indeed, in regard to the other impu- 

 rities named, the sense of taste is a tolerably safe guide. A water 

 is not likely to be injurious to health so long as it has no taste; 

 but this rule is not at all applicable to the case of the contami- 

 nation of water with lead. I think water containing no more 

 than l-20th of a grain of lead to the gallon had better be avoided, 



