NEPEAN WATER ON TUBES AND BOILER PLATES. 195 



IV. Means of ascertaining the amount of dissociation of the 

 solids at temperatures above the boiling point of water. 

 V. Practical corroding test. 

 VI. Practical incrusting or scale test. 



By the analysis of tlie water under consideration it will be 

 seen that the latter contains only some seven grains of total solid 

 matter. This consists of organic matter of a peaty nature, and 

 mineral matter consisting of alkaline chlorides and chlorides of 

 the alkaline earths. Nitrates are also present, the amount being 

 somewhat under .05 grain of HNOg per gallon. 



Concentration by heat, i.e., evaporation at the ordinary atmos- 

 pheric pressure, decomposes the nitrates to some extent, so that 

 concentration in vacuo is necessary to ensure the correct 

 estimation of the nitrates from a residue, the estimation of the 

 nitrates by Schultz' or Schlcesing's methods invariably yielding 

 higher results. 



The reduction of the nitx'ates in boilers at high pi'essures 

 brings about the dissociation of the salts and consequent corrosion 

 of the boiler plates. Water heated in sealed tubes with iron 

 show this in a marked degree. The action, moreover, takes place 

 at the ordinary temperature and pressure, time being of course 

 an important factor in the phenomenon. 



The water was found to exert a decidedly corrosive action on 

 iron plates 'at all temperatures between 60° and 212° F. at the 

 common atmospliei'ic pressure. A quantity of iron weighing 

 10G.146 grains was placed into a pint of boiling water and 

 maintained at the same temperatui'e and pressure for one hour. 

 The loss was found to be .0138 grain per hour. One gallon 

 therefore loses .1104 grain of metallic iron, and 1,000 gallons 

 will eat away 110.4 grains, and 63,400 gallons would consume 

 a pound of iron. 



