GO Mr. H. Medlock on the Reciprocal Action of Metals 



No. I. No. II. 



Not treated Treated 



with iron. with iron. 



Lime 7-280 6-173 grs. per gal. 



Magnesia 0-634 0-543 



Irou oxide 0027 trace 



Chlorine 1-052 1-047 



Sulphuric acid 2-343 5-302 



Silica 0-624 0-277 



Matter volatile on ignition . 2*126 1-108 „ 



Phosphoric acid .... traces traces 



Sodium 0-684 0-678 ,, 



Potassium 0-321 not determined 



Ammonia traces none 



Sulphuretted hydrogen . . distinct traces none 



Nitrous acid none traces 



Nitric acid traces traces 



Total solid residue obtained! 21>8753 18-295 

 by direct evaporation . J 



These analyses exhibit, at first sight, comparatively little dif- 

 ference in the quantities of mineral constituents, but on examining 

 them carefully, we find that in the ordinary water there are, in 

 addition to a large quantity of organic residue, distinct traces of 

 sulphuretted hydrogen, while in the water which has been in con- 

 tact with irou, no traces of this poisonous gas exist. Moreover, 

 in the ordinary Thames water, there are marked traces of am- 

 monia, while in the water treated with iron, no trace of this base 

 remained, the ammonia having been converted into nitrous acid. 

 The great increase in the quantity of sulphuric acid, from 2-343 

 grs. to 5-302 grs. per gallon, is very remarkable, and probably 

 is owing to the oxidation of sulphuretted hydrogen, or sulphurets 

 pre-existing in the water. This, however, requires further inves- 

 tigation, and a series of experiments I am now engaged in, will, I 

 h.opc, determine this question satisfactorily. In the above ana- 

 lyses, for obvious reasons, I have substituted for the indefinite 

 term "organic matter," the expression " matter volatile on ig- 

 nition." 



From the residue of one gallon of the water, 2-126 grs. were 

 expelled by ignition, while from the residue of one gallon of the 

 water which had been in contact with iron, only 1-108 gr. was 

 volatilized. Moreover, the residue of the first water became 

 nearly Ijlack when heated, while the residue of the second was 

 scarcely altered in colour, except at the edges, not-vvith standing 

 that it lost a little more than a grain by the ignition. This loss 

 was not organic matter, as no charring was observed, but was due 



