160 



CHEMISTRY. (HOUSEHOLD.) 



hundred pounds pressure to the inch. All or- 

 ganic matter is destroyed, and the water is 

 made perfectly pure. 



Domestic Chemistry. Dr. Percy F. Frankland 

 records the results of experiments he has made 

 with a view to discover whether and to what 

 extent micro-organisms may he removed from 

 water by submitting it to some of the various 

 processes of treatment which are in vogue for 

 its purification. The number of organisms 

 present in the waters was determined, both 

 before and after treatment, by the method of 

 Koch. The organisms developed in diluted 

 urine were made the objects of the experi- 

 ments. Filtration through fresh greensand, 

 highly ferruginous, completely sterilized the 

 water. After thirteen days of continued ac- 

 tion, the original power of the greensand was 

 found to have broken down ; but the filter was 

 still arresting a considerable proportion of the 

 organisms. With spongy iron, sterilization was 

 complete, both at the beginning of the filtra- 

 tion and after twelve days of continuous action. 

 With animal charcoal, perfect sterilization was 

 effected at the beginning, and after twelve days 

 of continuous filtration ; but at the end of a 

 month the filter delivered water more highly 

 impregnated with organic life than that with 

 which it was supplied. Brick-dust failed to 

 wholly remove the organisms. Coke was found 

 to possess filtering powers second only to those 

 of spongy iron. At the outset the result was 

 equally perfect with both, and even at the close 

 of five weeks' continuous work the coke re- 

 moved a large proportion of the micro-organ- 

 isms present in the unfiltered water. The ob- 

 ject of a second class of experiments was to 

 ascertain whether the organisms might not be 

 removed by agitation with the same substances 

 used in the filters, and then allowing them to 

 subside. An u exceedingly marked " reduction 

 was obtained by shaking with spongy iron, and 

 greatest when the agitation was continued for 

 only a minute ; with chalk, " a very large re- 

 duction." The efficiency of animal charcoal 

 was "very markedly greater" than that of 

 chalk. Simple agitation with coke for fifteen 

 minutes was sufficient to remove all organisms. 

 As in the agitation experiments the water for 

 examination was always taken from the clear 

 upper layers, Dr. Frankland tried experiments 

 to ascertain whether the micro-organisms would 

 not, by subsidence alone, separate from these 

 layers without the influence of solid particles. 

 The result showed that, so far from any tend- 

 ency of this kind existing, the tendency was 

 for a very rapid increase in the number of 

 micro-organisms. From Clark's process of soft- 

 ening water by means of lime, results were ob- 

 tained showing that in it we possess a means 

 of greatly reducing the number of suspended 

 organisms. Dr. Frankland's general conclu- 

 sion is that, although the production in large 

 quantity of sterilized potable water is a matter 

 of great difficulty, involving the continual re- 

 newal of filtering materials, there are numer- 



ous methods of treatment which secure a 

 large reduction in the number of organisms 

 present. 



Sir Frederick Abel, after investigation of a 

 number of accidents arising from explosions of 

 petroleum-lamps, has arrived at several defi- 

 nite conclusions respecting the causes of such 

 explosions and certain circumstances that may 

 tend to favor their production. If a lamp of 

 which the reservoir is only partly full of oil be 

 carried or rapidly moved from one place to an- 

 other, a mixture of vapor and air may escape, 

 and, becoming ignited in the flame, determine 

 the explosion of the mixture contained in the 

 reservoir. A sudden cooling of the lamp, by 

 its exposure to a draught, or by its being blown 

 upon, may give rise to an inrush of air which 

 will increase the explosive properties of the 

 mixture contained in the reservoir, and the 

 flame may at the same time be drawn or forced 

 down into contact with it. The glass may also 

 be cracked by the sudden cooling, and let the 

 oil escape. These effects may sometimes be 

 produced by blowing down the chimney to ex- 

 tinguish the light. If the oil be low-test, the 

 explosion may take place the more readily, but 

 is relatively feeble, because the air will have 

 been largely expelled from the reservoir by 

 the generation of petroleum-vapor. If the 

 flashing-point of the oil is high, the vapor will 

 be less readily or copiously produced, but the 

 mixture of vapor and air in the reservoir may 

 be more violently explosive, because the propor- 

 tion of air in it will be greater. Experiments 

 have also shown that a lamp containing an oil 

 of a high flashing-point is more likely to become 

 heated than one containing a comparatively light 

 and volatile' oil, in consequence of the much 

 higher temperature developed by the combus- 

 tion, and of the comparative slowness with 

 which the heavy oil is conveyed by the wick to 

 the flame. It therefore follows that safety in 

 the use of mineral-oil lamps is not to be secured 

 simply by the employment of oils of very high 

 flashing-point, and that the use of very heavy 

 oils may even give rise to dangers which are 

 small, if not entirely absent, with oils of com- 

 paratively low flashing-points. From these 

 principles, and as the result of his experi- 

 ments, the author derives the following sug- 

 gestions, attention to which may serve to re- 

 duce the risks of accidents in the use of petro- 

 leum and paraffine oil: The reservoir of the 

 lamp should be of metal, and there should be 

 no opening or channel of communication with 

 it at or near the burner, unless it be so guarded 

 or so small that it can not be permeated by 

 flame. The wick should be of soft texture and 

 loosely plaited, should fill the entire space of 

 the wick-holder without being jammed in it, 

 should be thoroughly dried, should be but 

 little longer than to reach the bottom of the 

 reservoir, and should never be immersed to a 

 less depth than about one third of the total 

 depth of the reservoir. The reservoir or lamp 

 should always be almost filled before use. If 



