518 keport— 1878. 



potassium being carefully purified from iodate, the solutions keep very well, and 

 are reliable. _ The iodide should be dissolved as required. The Vartry water does 

 not give indications with the tests as a rule without concentrating it. I subjoin 

 the results of my experiments on the 3rd of August : — 



1. Water evaporated to ^ at 100° 0. gave a very striking indication of nitrites, 

 besides nitrates. 



2. Evaporated in a vacuum to 5 it gave no indication. 



3. Evaporated in vacuo to \ it gave an indication of nitrites and nitrates. 



In January 1878, the Vartry gave no indication of nitrites, but contained, as 

 usual, nitrates, and gave an indication on evaporating to one-half. We see by 

 these observations that evaporation tends to reduce the nitrates. Also that from 

 fermentative action changes occur at certain periods of the year, which result in 

 the reduction of nitrates to nitrites. 



We see also that these nitrates and nitrites are present in very minute quantities. 

 I have never found 0-1 of a grain per gallon said to be present in Loch Katrine 

 water ; the highest amount I have ever found being 0-06, determined by the 

 aluminium process. But still, when these salts are rapidly concentrated, as they 

 are in the feeding of high-pressure steam boilers, the nitrogen salts become very 

 serious items of corrosion, owing to the ease with which the acidulous radicals are 

 dissociated at high temperature, e.q. — ■ 



NaN0 3 = NaNO„ + 0. 



2NaNO„ + H 2 = 2(NaHO) + 2NO. 



2NO + Fe = FeO + N 2 0. 



I exhibit a boiler plate, which is not eaten away by the corrosive action of 

 water, but the corrosion is determined by the steam of the Vartry water. I also 

 exhibit glass corrosion produced by the same means. 



^ Some experiments were instituted in sealed tubes which bear strikingly upon 

 this subject, and which I now beg to place before the section. 



_ No. 1. — In this experiment distilled water was boiled in a tube and a piece of 

 bright wire inserted. The tube was then sealed, after the air had been exhausted. 

 It is now some months old, and it will be observed that there is comparatively no 

 action. We are to infer, therefore, from this experiment, that at ordinary tempera- 

 tures water is without the slightest action upon iron in vacuo. We all know how 

 rapidly iron is oxidized in the presence of water containing air. 



No. 2 is iron sealed up in vacuo with Vartry water, and submitted to high- 

 pressure steam at 301bs. to the square inch. The action is sharp and well marked, 

 theresults being the production of ferric oxide in considerable quantities, and mag- 

 netic oxide. The latter can be recognised on applying a magnet outside the tube. 



The third tube was a similar experiment with pure water, containing - l grain 

 per gallon of nitrate of potassium. This also was sealed in vacuo. The results 

 are almost identical with the second experiment, only that more magnetic oxide 

 seems to have been formed. The fourth experiment was one in which a nitrite was 

 substituted for the nitrate. Here nothing but ferric oxide was formed of a peculiar 

 bright colour, and in scales. 



That the corrosion of the boiler plate mainly proceeds from the nitrogenous 

 molecules, I think there can be little doubt. But the quantity of these acidulous 

 radicals being very small, any of the alkaline preservations would remedy this 

 corrosive action. If, however, neglected, these nitrogenous acidulous radicals would 

 almost certainly lead to mischief, and therefore they are imminent sources of 

 danger. 



8. On a New Process of Photo-Chemical Printing in Metallic Platinum. 



By W. Willis, jun. 



