214 D.WMie— On the 3Iuddi/ Water of the Hu^U. [No. 4, 



July, 1870, is a short abstract from the * Comptes Rendus' of the Academy 

 of Sciences, of 20th June 1870, of a paper by Dr. C. Schloesing on the same 

 subject, in which, it is stated, he refers to river waters contaminated with clay 

 being readily clarified by 1000th part of chloride of calcium or other salts 

 of lime, and being then readily filtered, while previously they rapidly choked 

 the filter. He refers to several rivers, such as the Rhine in its lower course 

 and the Durance which supplies Marseilles, as being notorious for this peculi- 

 arity. Then in the same Journal of 12th May, 1871, Mr. Skey notices this 

 as a re-discovery on the part of Schloesing, and says that 1 grain of chloride 

 of calcium is sufficient for 10 ounces of muddy water or 50,000 grains, an 

 evident misprint for 5000 grains. He also notices a paper on the so-called 

 molecular movements of microscopic particles by Professor Jevons, who has 

 some theory about this coagulation of clay being due to the water becoming 

 by such addition a conductor of electricity, and the clay particles charged 

 with electricity. 



Besides all these direct observations, there is a phenomenon which had 

 long (long before these observations were made) come under the observation 

 of chemists in filtering and washing certain precipitates and sediments, 

 namely, that for a time, while there is saline matter present in solution, the 

 filtered liquid comes clear, but when, by continuing to wash such substances 

 by distilled water, these saline matters become much reduced in quantity, 

 then the filtered liquid flows muddy, the solid substance passing in a state 

 of very fine division through the pores of the filtering paper. The chemist to 

 avoid tliis adds a proportion of some saline substance (such as chloride of 

 anmonium or muriate of ammonia) which will not interfere with his subse- 

 quent proceedings, and so is enabled to wash the sediment or precipitate free 

 from everything except the substance which he has added. He can get rid 

 of this afterwards by other means if it be necessary. This peculiarity espe- 

 cially occurs with clays and substances more or less analagous to them, such 

 as Zirconia and Titanic acid. Another illustration is given when we at- 

 tempt to extract the saline matters soluble in water from clayey soils. 

 When the soil is first mixed with distilled water and allowed to settle, the 

 supernatant liquor may be clear : if this be poured ofl^" and more distilled 

 water be mixed with the residue, it will not settle and clear so readily, and if 

 the process be repeated, it may take a very long time to do so. Just in 

 proportion as the saline matter is removed, the fine clay separates with 

 greater difficulty from the pure water. 



It is to be observed that the substances here referred to, namely, neutral 

 salts, are just the same sort of matter that exists in natural waters in small 

 quantity. Reflecting on the difficulty, with the impression of the above- 

 mentioned facts on my mind, on or about the 1st August last, the ques- 

 tion occurred to me : How small a quantity of such substances is sufficient 



