September ], 19]]] 



SCIENCE 



259 



that mechanical means have been found for 

 separatinf^ the ingredients of whole groups 

 of chemical compounds, and the modern 

 view that the amount of mechanical work 

 necessary to bring about the separation is 

 the only measure we have of the affinities 

 that brought about their union. 



Solutions, in some of these books, are open- 

 ly classed with the mechanical mixtures, and 

 in all are spoken of in language applicable 

 properly to the latter alone. In brine, for 

 instance, salt and water are said to ' ' retain 

 their properties unchanged." Not to 

 dwell on the ridiculous illustration found 

 in many, that ' ' the salt retains its taste ' ' — 

 as though dry salt could be tasted — this as- 

 sertion ignores the lowering of the vapor 

 tension of the water, and consequently the 

 lowering of its most characteristically 

 "chemical" property, its chemical poten- 

 tial, or power to enter into reaction. Pure 

 water, to give an instance, reacts at 30° C. 

 with the chemical compound sodium sul- 

 phate to form its hydrate Glauber salt, 

 also a chemical compound; the reaction is 

 thus "chemical" in the strictest sense of 

 the word, as none but chemical compounds 

 are involved; when combined with salt to 

 form a saturated brine, however, this power 

 of the water is lost. 



The change of chemical properties which 

 is ignored when a solution is formed, is ex- 

 aggerated when a chemical compound is the 

 residt of the uxiion; in that case, "an en- 

 tirely new substance" is produced, whose 

 constituents have "lost their characteristic 

 properties." Now, surely, the most char- 

 acteristic property of oxygen is to oxidize ; 

 does it lose the power of oxidizing carbon 

 by combining with copper? if so, how are 

 the "combustions" of the organic labora- 

 tory to be accounted for? Does it lose this 

 power by combining with hydrogen? if 

 so, what about the manufacture of water 

 gas? In truth, as was the case with water 



in brine, the characteristic properties of 

 oxygen in copper oxide and in water are 

 lessened, not lost. It is not even safe to 

 say that chemical combination always 

 brings about the greater change; as Bell 

 has shown, water combined in washing 

 crystals is more ' ' itself ' ' than when sucked 

 up by a dry cigar. 



It might be urged in extenuation of this 

 exaggeration, that, after all, chemistry, like- 

 other sciences, works by classification, and 

 that children like distinctions sharp. The- 

 heroes of boys' books are heroes every inch;, 

 their fools and villains likewise Simon 

 pure; and all agree that problem plays — 

 where the problem is to tell the villain 

 from the fool and to guess who is the hero. 

 — are not for such as they; a little exag- 

 geration might therefore be defended as' 

 good pedagogy, and suited to the childish 

 mind. This might be a good excuse, if it 

 were not that (no doubt in order to be 

 up to date) the texts while denying con- 

 tinuity, include much of the experimental 

 evidence which has forced this conception 

 into our science. The result is that they 

 contradict themselves, and involve the 

 w^hole subject in a maze of vagueness and 

 mystification foreign to the scientific 

 spirit; an example or two of each will be 

 given, beginning with a typical instance 

 of self-contradiction. 



Most of the texts give their readers the 

 impression that gunpowder is regarded as 

 a mixture containing niter, or that sul- 

 phur and iron filings form a mixture con- 

 taining sulphur, or that the high-school 

 grocers' mixture of sand and sugar is a 

 mixture containing sugar because the 

 niter or the sulphur or the sugar can be 

 leached out or dissolved by water or by 

 carbon bisulphide, that is, by liquids which 

 dissolve those solids when pure. It is 

 sometimes added that the ingredients of 

 the mechanical mixture have thus been 



