332 SCIENCE PROGRESS 



" It may safely be assumed that all metals and alloys, when 

 plunged into dilute acids or into water, either pure or con- 

 taining salts in solution, tend to pass into solution." This is 

 the opening sentence in the fourth section of the Report referred 

 to above. Nothing of the sort can be assumed : so far as we 

 know at present, nothing happens in the absence of an electro- 

 negative element from the system ; the evidence is overwhelming 

 that water pure and simple is without action. 



In the fifth section we are told that Carnelly has shown that 

 copper is soluble to a minute extent even in distilled water if 

 oxygen be present. The reporter remarks that Carnelly's result 

 is unexpected but is supported indirectly by other experimental 

 evidence ; he is not sufficiently clear on the theoretical side to 

 realise that attack must have been determined by the presence 

 of traces of acid in the liquid. 



In the case of the copper alloys, we need information on 

 all sorts of fundamental points. What is brass ? Is it — within 

 certain limits of composition — a compound of copper and zinc 

 or are the molecules of the metals still possessed of properties 

 which are characteristic of them when alone ? Or in what 

 proportions are the metals present separate and combined ? 

 Micrographic research is teaching us much on these points but 

 there is a tendency to exaggerate its relative importance. A 

 new nomenclature is being introduced, as in the case of steel — 

 to the confusion of the practical man : but we don't get to 

 grips with the real problems. We need to look at the matter 

 both from the chemical and from the morphological side — and 

 in neither case superficially ; before all things also we need to 

 introduce a large element of common sense into the inquiry and 

 to cast pretence aside. 



Many years, ago Ackworth and I showed that a brass con- 

 taining about 70 per cent, of copper behaved as copper towards 

 nitric acid — as if by association with the copper the zinc were 

 transmuted into copper. It is well known that much heat is 

 given out when the metals are alloyed, so that evidently the 

 zinc parts with some of its intrinsic energy in the process and 

 is reduced at least to the level of copper. Long ago also it 

 was shown by Laurie that the electromotive force developed 

 by zinc-copper alloys was only that given by copper up to the 

 point at which zinc was present in a proportion beyond that 

 required by the formula Cu 2 Zn. Probably, therefore, it is only 



