62 Mr. II. Medlock on the Reciprocal Action of Metiils 



A second quantity of water was ])Iaced in bottles with tlie 

 same quantity of iron and allowed to remain for forty-eight 

 hours. When filtered and evaporated, the residue, like the pre- 

 ceding, was perfectly colourless, and when weighed gave, — 



Total solid residue 10-1384 grs. per gal. 



Including matter volatile on ignition. 0'1321 „ 



Hardness 6° 



From these experiments, it appears that by submitting water 

 to a Inrge surface of iron, and allowing it to remain in contact 

 for a longer period, nearly every particle of organic matter, 

 whatever may have been its origin, is entirely removed from the 

 water. The trifling loss on ignition (0-2 gr. per gallon) is evi- 

 dently due to the volatilization of those mineral constituents 

 which have been proved to volatilize at a red heat. 



Keeping in view the facts above stated, we shall be enabled to 

 perceive that the method of analysis hitherto adopted for deter- 

 mining the fitness of a water for domestic purposes, is in several 

 respects defective. According to the latest and most approved 

 method of analysing a water to ascertain its dietetic value, a 

 given quantity is evaporated in an open porcelain dish, over a 

 gas-flame, nearly to dryness. The residue is transferred to a 

 small dish of platinum, and evaporated to perfect dryness on 

 a water-bath. It is now heated in an air-bath at a tempera- 

 ture of 218° F. (120° C), to expel the last traces of moisture 

 and the water of hydration belonging to sulphate of lime. The 

 residue is weighed, and the result is recorded as the weight of 

 the " total solid residue." The dish containing the residue is 

 now ignited over a gas-flame, to burn off the " organic matter." 

 The residue is moistened with a ievf drops of solution of car- 

 bonate of ammonia to replace any carbonic acid which may have 

 been expelled from the lime by the ignition. It is dried again in 

 an air-bath at the same temperature as before, and weighed several 

 times till the weight remains constant. The loss of weight 

 occasioned by the ignition, is assumed to represent the quantity 

 of "organic matter" originally present in the water. In the 

 residue are determined the proportions of silica, iron, alumina 

 and phosphates, lime, and magnesia. 



A second portion of water is evaporated in a similar manner, 

 and in this are determined the chlorine aiul sulphuric acid. A 

 third portion is evaporated, and in this arc determined the alkalies. 

 Finally, the acids and bases arc recorded as associated together 

 in the order of their respective affinities, and the analysis is con- 

 sidered complete. 



It is obvious that this nu thod of analysis docs not determine 

 with certainty the auiount of putrescible organic matter originally 



