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agencies in the purification of water, residing in the vegetable 
and animal life inhabiting it, which co-operate in consuming 
effete matter with surprising rapidity. 
Prof. Wurtz concluded by recommending in high terms 
the proposition to convert the Morris canal from an un- 
profitable channel of navigation into a source of pure water- 
supply for the two cities above named. 
Pror, A. R. Leeps read a paper “On the Dissociation of 
certain Compounds at very low T'emperatures.”’* 
Fittiz, Debbits, and others, have shown that salts of 
ammonia, especially the nitrate, sulphate, chloride, oxalate, 
and acetate, liberate ammonia when their solutions are 
boiled, and also when a current of an inert gas is passed 
through their saturated solutions at ordinary temperatures, 
or even at 0°C. Prof. Leeds then showed :— 
1st. That it is not necessary to change the atmosphere in 
contact with the particles of the salt held in solution, by 
passing a current of an inert gas, in order to induce dissocia- 
tion at temperatures below the boiling point. 
2d. That there is a certain fixed temperature, which is 
different in the various salts, at which the dissociated con- 
stituent can be detected and recognized by sufficiently delicate 
tests, 
3d. That it is highly probable that the dissociation of these 
salts in solution is analogous to the evaporation of the solvent, 
and that while it arrives at a maximum (under ordinary 
atmospheric pressures) at the boiling points of their saturated 
solutions, yet it takes place in a diminishing proportion at 
much lower temperatures, and in some cases even below their 
freezing points. 
The reagent employed in these experiments was alizarin, 
which will readily detect 1 part of soda in 38,000,000 of 
water. Prof. Leeds gave a table containing the results of 
about twenty determinations, the dissociation of ammonic 
oxalate being that observed at the lowest temperature. 
* Published in full in the American Journal of Science, March, 1874. 
