202 



KNOWLEDGE ♦ 



[Sept. 5, 1884. 



or not. And with each one the state of support was such 

 that he could not fall so long as the rigidity continued. 



Many questions and conclusions of intense interest are 

 rassocialed herewith, but for the present we must leave them 

 untouched. W. A. O. 



THE INTERNATIONAL HEALTH 

 EXHIBITION. 



XIV.— WATER AND WATER-SUPPLIES— (conlinwect). 



IN our remarks upon the " Grant Revolving Ball Water 

 Filter," we drew the attention of our readers to this 

 remarkable contrivance as being one which is peculiarly 

 adapted to the purification of tolerably wholesome water, 

 and in doing so provoked a reply from the inventor, who, 

 it is but just to state, has furnished us with ample evidence 

 that the instrument is capable of dealing effectively with 

 *ven filthy and highly impure waters. We have tested 

 the apparatus, and find the filtrate of our experiments all 

 that could be desired for drinking and for culinary purposes. 

 In cleansing the filter by reversion of the ball, it is some- 

 what surprising to find, in spite of all theoretical rea.soning 

 to the contrary, that the carbon is not approximately, but 

 thoroughly cleansed, and the operation is so simple that it 

 raay be put into action every time that the filter is used, 

 although in reality it does not require such attention more 

 than once or twice daily. 



On a large scale, these filters might be fixed with ad- 

 vantage to public drinking-fountains and street-service 

 hydrants, as suggested by the Home and Colonial 2rail,* 

 when " the policeman on his beat could cleanse them at 

 intervals by merely turning a handle in passing. This 

 handle could be constructed, in filters destined for public 

 hydrants, to allow of its being locked, to prevent damage 

 from mischief." 



Type IV.—" The Spongy Iron Filter."— The researches 

 ■of Prof. Gustav Bischof, which led to the employment of 

 -spongy iron as a filtering medium of value, are carefully 

 recorded in the " Proceedings of the Royal Society,"! and 

 •one of the most important benefits derived from its use is 

 shown to be due to its destructive action upon organic 

 germs. In his report to the company. Professor Frank- 

 land, F.R.S., writes as follows: — +" Taking into account 

 the extremely bad quality of the raw material at the time 

 of my visit, I consider this result to be eminently satisfac- 

 tory from a purely chemical point of view ; but there is 

 another factor involved in this result which has still greater 

 weight with me in the comparison of the water before and 

 after treatment, viz., the circumstance that the water has 

 Ijcen passed through a material which is absolutely fatal to 

 bacteria and their germs. It has been proved by Prof. 

 Bischof § that water which has passed through spongy iron 

 is entirely free from bacterial germs, and by my pupil, 

 Mr. F. Hatton, working in my laboratory, that spongy 

 iron is the only known substance applicable to the treat- 

 ment of large volumes of water which immediately destroys 

 living bacteria. "II We need scarcely add that the immunity 

 from zymotic disease, secured through the use of so 

 valuable an apparatus, ought to be a powerful argument 

 in favour of its general acceptance as a household necessity. 



The internal mechanism of the filter may be readily 

 understood by a reference to the figure here annexed 



* July 18, 1881, p. 5. 



t " On Putrescent Organic Matter in Potable Water," No. 180, 

 1877; No. 186, 1878. 



X Report to the Directors of the " Spongy Iron Water and 

 Sewage Purifying Co.," August 8, 1882. 



§ Op. cit., xxvii., p. 258. 



]| " Journ. Chemical Society," x.'vxi.'i.. p. 2i7. 



(Fig. 27), from which it will be gathered that it is entirely 

 different in plan from any of the appliances which we have 

 hitherto noticed. The following description, which hae 

 been kindly furnished to us Vjy the company, will enable 

 the reader to gain an insight into its detailed structure : — 

 " (1) The unfiltered water is supplied by means of ball-cock, 



Fig. 27. — Bischof's Spongy Iron Special Ball-cock Filter. B., ball- 

 cock ; U., unfiltered water; V., ecrew-valve; I., spongy iron; S., 

 S'., S"., prepared sand ; F., filtered water; T., stop-cock. 



B, with glass-ball, G, and screw-valve, V ; the latter serves 

 to shut off the water in any emergency. The ball-cock 

 requires no fixing to a wall, but is fastened to the side of 

 the filter-case by screws, R ; it is connected with the water- 

 supply or cistern by india-rubber or other tubing, P. The 

 water passes through the several layers of filtering materials, 

 which are enclosed betweeu the perforated plates, C, C', C". 

 It is next collected in a small well, or regulator bowl, and 

 thence passes into a tin tube, provided at its outer end 

 with a screw-cap, A. The lateral opening, X, in the side 

 of the tube forms the only communication between the 

 upper part of the filter and the reservoir for filtered water. 

 The flow of water is thus controlled by the size of such 

 opening. (2) The supply of water to this filter should be 

 sufficient to insure the materials remaining covered with 

 water." 



Spongy iron is metallic iron in a state of excessively fine 

 division, which renders it sufficiently porous to admit of 

 the percolation of water. It takes the place of the carbon 

 of other filters, and acts virtually in the same way. Apart 

 from its obvious property as a mechanical strainer, it is a 

 chemical purifier. It counteracts lead contamination,* 

 reduces the hardness of water,! and, as we have before 

 noted, is strongly antise])tic as far as organic matters are 

 concerned. Mr. F. Hatton has shown : — I (1 ) " That it acts 

 as a very powerful reducing agent on the carbon compounds 

 composing the organic matter dissolved in water. In some 

 cases marsh gas itself was produced — probably the organic 

 matter was first oxidised to carbonic acid (C0„), and then 

 the action of the metallic iron on this gas gave rise to 

 marsh gas (CH^) by the ordinary decomposition of water. 

 (2) The organic nitrogen is in nearly all cases reduced 

 to ammonia." 



In its passage, the water dissolves a small quantity of 



* " Joiu-nal Eoval Agricultural Society," vol. xi., part 1, 1875, 

 p. 158. 



t " Rivers Pollution Commission," 6th report, p. 220. 

 I " Journal Chemical Society," May, 1881. 



