Jan. 6, 1888.] 



SCIENTIFIC NEWS. 



13 



THE ALLEGED PURIFICATION OF 

 WATER BY FREEZING. 



THERE prevails a notion — to call it a superstition 

 might seem discourteous — that if a bodj' of impure 

 water is exposed to a temperature below the freezing- 

 point (32° Fahrenheit) the ice formed will be absolutely 

 pure or very nearly so, whilst the impurities will be 

 found collected in that portion which remains liquid. 

 What may have been the origin of this supposition it 

 might be very difficult to ascertain. But we find men 

 of high standing giving it their sanction. Professor 

 Tyndall is reported to have said that he could get 

 no purer water than pure melted ice. In the first 

 volume of Miller's "Chemistry" we read: "Indeed, 

 water in the act of freezing becomes completely sepa- 

 rated from everything which it held in solution." 



On the faith of such authorities freezing was even pro- 

 posed as a means of dealing with the sewage of London. 

 It was to be exposed to intense cold and the greater 

 part of it converted into ice. This, being supposed pure, 

 was to be sold to fishmongers, and in short to all trades- 

 men who use ice in their business. The unfrozen part, 

 retaining all the impurities in a concentrated form, might 

 be easily used for irrigating meadows, etc. Fortunately, 

 the economical aspect of this scheme appeared so unpro- 

 mising, that it was never tried on a large scale. 



But in a number of very careful laboratory-experi- 

 ments, the ice when thawed was found rich in organic 

 pollution. Our attention has been recalled to this sub- 

 ject by certain interesting observations made in the 

 United States. In that country the use of ice in connec- 

 tion with food and drink is much more common than 

 with us, and the supply is not always obtained from 

 pure waters. Hence serious mischief has arisen, and 

 sanitary chemists have been induced to make careful 

 analyses of ice and ice water. Grape-sugar and white 

 of egg in known quantities were dissolved in v>'ater, 

 which was then allowed to freeze. The ice was found 

 afterwards to contain, on the average, rather moie than 

 half the proportion of these substances which had been 

 added to the water. 



A very interesting difference was, however, noticed. 

 Ice from water which holds in solution mineral matter, 

 such as common salt, copperas, alum, or the like, will 

 contain less of these substances than the water from 

 which it was obtained, and by alternately freezing, re- 

 dissolving in distilled water, and again freezing, nearly 

 all the mineral matter may in time be removed from the 

 ice. 



With the organic impurities — the decomposing re- 

 mains of plants and animals — the process is rather re- 

 versed, a pound of ice from polluted rivers containing 

 more of such matter than a pound of the original water. 



Thus, then, we see that water cannot be freed from 

 its organic impurities by any freezing process. But 

 what of foreign matter which is suspended in a solid 

 form and not dissolved at all ? Here, surely, every man 

 and woman in the world blessed with eye-sight can 

 make answer. Who has not seen in a frozen pool 

 leaves, sticks, chips, the remains of dead insects, dust 

 and bits of paper embedded in the ice ? And if this is 

 the case we may surely be convinced that smaller por- 

 tions of solid matter, often much more offensive and 

 dangerous than the above, will not be wanting. An 

 appeal to the microscope will at once verify this conclu- 

 sion. 



But there is one form of solid or suspended impurity 

 possible in ice which is of especial importance — patho- 

 genic or disease-germs. No degree of cold with which 

 we are acquainted can destroy these minute beings, 

 though it may temporarily suspend their activity. 

 Water from the clearest ice may swarm with them, 

 though no want of transparency is perceptible in either. 

 But it may be asked. Is there more risk of finding such 

 microbia in ice than in water ? We must say. Yes. 

 Water may be, and often is, obtained from deep wells 

 which has never been exposed to the atmosphere, and 

 which contains no organic matter to serve for the nour- 

 ishment of germs. But ice can only be obtained natur- 

 ally from waters which have been spread out to the air, 

 and into which consequently dust and dirt of various 

 kinds must have fallen. So impure is the air that a pro- 

 minent sanitarian even speaks of " previous sewage con- 

 tamination " in the rain ! It would, of course, be pos- 

 sible to conduct the water from some deep well into a 

 freezing machine, all the internal parts of which should 

 be artificially sterilised. But such ice is not to be had. 

 All that can be done, therefore, for the present is to 

 obtain ice only from the purest lakes or streams far 

 apart from human dwellings and into which no sewage 

 can possibly have found its way. 



Some sad cases have occurred in America from the 

 neglect of such precaution. In 1875, Rj^ Beach, in 

 New Hampshire, was attacked by an epidemic of dysen- 

 tery. Professor Nichols, of Boston, traced this disease 

 conclusively to ice. No one was taken ill, save such as 

 had been using a supply of ice from one particular 

 source. 



In 1879 another epidemic of dysentery broke out in 

 Washington, Connecticut, and was traced by Professor 

 Raymond, of Long Island College, and Dr. Brown, of 

 Litchfield, to the ice which had been employed. Here, 

 again, when the supply of that quality of ice was stopped 

 the disease ceased, and only those suffered from it who 

 had been indulging in the suspected ice. Here, then, 

 is evidence which can be fully understood by every one, 

 however little he may be acquainted with the niceties of 

 microscopical research. 



The epidemic of typhoid fever which broke out at 

 Plymouth, Pennsylvania, in 1885, was produced by 

 germs which must have been frozen up all the winter. 



The most recent case of this kind was the intestinal 

 affection with which most of the European visitors to 

 the late Medical Congress at Philadelphia were attacked. 

 They had conformed to the American custom of drink- 

 ing iced water at dinner, and suffered accordingly. 



It is startling to learn that most of the ice consumed 

 in New York is obtained from the river Hudson below 

 the towns of Troy and Albany. In these two towns the 

 yearly average of deaths from typhoid fever is seventy- 

 five, and all their dejecta are carried into the river. 



Surely we do not go too far if we bid our readers 

 beware of ice and of ice-water. 



Man-chester.-— The Council of the Technical School have 

 recently purchased a valuable collection of apparatus, of 

 German manufacture, illustrative of the principles of 

 mechanism, and of sound, light, and chemistry in their tech- 

 nical applications. They have also made arrangements for a 

 course of twelve lectures on " Chemical Engineering," to be 

 delivered by Mr. G. E. Davis, late Government Inspector of 

 Alkali Works. This school enjoys considerable prosperity, 

 and is at present attended by 2,304 students, as compared 

 with 2,136 at this time last year. 



