By actual experience I have been able to prove that at least 25 sections of electrodes should be in series and across any one of these sections the potential difference need not be greater than 1.8 volts, the current being of any desired amount, according to the surface of plates used.

The electrical measurements taken by Dr. John Hopkinson during these experiments for the Electrical Purification Association, to whom I had sold my patents, entirely corroborated my contentions as to E.H.P. used, and agreed with the measurements of the managing electrician, Mr. Octavius March.

The process was then thoroughly investigated by Sir Henry Roscoe, who had control of the works for one month.  He reports as follows: 

“The reduction of organic matter in solution is the crucial test of the value of a purifying agent, for unless the organic matter is reduced, the effluent will putrefy and rapidly become offensive.

“I have not observed in any of the unfiltered effluents from this process which I have examined any signs of putrefaction, but, on the contrary, a tendency to oxidize.  The absence of sulphureted hydrogen in samples of unfiltered effluent, which have been kept for about six weeks in stoppered bottles, is also a fact of importance.  The settled sewage was not in this condition, as it rapidly underwent putrefaction, even in contact with air, in two or three days.

“The results of this chemical investigation show that the chief advantages of this system of putrefaction are: 

“First.—­The active agent, hydrated ferrous oxide, is prepared within the sewage itself as a flocculent precipitate. (It is scarcely necessary to add that the inorganic salts in solution are not increased, as in the case where chemicals in solution are added to the sewage.) Not only does it act as a mechanical precipitant, but it possesses the property of combining chemically with some of the soluble organic matter and carrying it down in an insoluble form.

“Second.—­Hydrated ferrous oxide is a deodorizer.

“Third.—­By this process the soluble organic matter is reduced to a condition favorable to the further and complete purification by natural agencies.

“Fourth.—­The effluent is not liable to secondary putrefaction.”

Mr. Alfred E. Fletcher also investigated the process subsequently, and reports as follows: 

“The treatment causes a reduction in the oxidizable matter in the sewage, varying from 60 to 80 per cent.  The practical result of the process is a very rapid and complete clarification of the sewage, which enables the sludge to separate freely.

“It was noticed that while the raw sewage filters very slowly, so that 500 c.c. required 96 hours to pass through a paper filter, the electrically treated sewage settled well and filtered rapidly.

“Samples of the raw sewage, having but little smell when fresh, stank strongly on the third day.  The treated samples, however, had no smell originally, and remain sweet, without putrefactive change.