OF ZINC AND ANTIMONY. 369 



equivalents of chloride of sodium, and also of intermediate , composition. He states, 

 moreover, that " Calloud, who first observed that the grape-sugar of honey combined 

 with chloride of sodium, found that the amount of the latter varied between 8.3 and 25 

 per cent." Staedeler refers the variation in composition to a mixture of the compound 

 of one with the compound of two equivalents of chloride of sodium, which he assumes 

 to be isomorphous. He adds, that it may be caused by " inclosed crystals of chloride 

 of sodium, although the eye could not distinguish any heterogeneous constituents." 



All the above compounds are examples of weak chemical affinity, accompanied by 

 large variations in composition without any change in the general crystalline form. It 

 is not meant to assert that the variations are identical in character with those of SbZug 

 and SbZng, but only that there is a strong probability that this is the case, which, in 

 the first two instances, amounts almost to a certainty. 



If variations in composition of such magnitude are possible when the force of chemi- 

 cal affinity is weak, it is highly probable that some variation may occur when the force 

 is strong ; and, whatever view may be taken of the cause of the variation, it will now 

 become a matter of importance to ascertain whether many discrepancies in analyses 

 hitherto referred to imperfections in the process may not be owing to the same cause 

 which influences the composition of the crystals of the two compounds of zinc and an- 

 timony. For this purpose it will be best to make several analyses of the same com- 

 pound, prepared under circumstances differing as widely as possible, and then to apply 

 to the resvilts Peirce's " Criterion for the Rejection of Doubtful Observations." Such 

 investigations will be greatly simplified by the tables prepared by Dr. B. A. Gould, Jr., 

 for facilitating the application of this criterion, to which I would refer all chemists 

 who are inclined to take up this line of investigation. 



I am well aware that, in announcing the existence of perturbations of the law of 

 definite proportions, I am calling in question one of the most fundamental dogmas of 

 chemical philosophy, and that the new doctrine will have to encounter prejudice on 

 this very ground. This law is so intimately associated in many minds with the atomic 

 theory, that to such absolute definiteness seems to be its essential characteristic. Never- 

 theless, I cannot but believe that, laying aside the prejudices which the theory begets, it 

 will be seen by all that the analogies of nature support the doctrine of variation as main- 

 tained in this memoir. The phenomena of none of the phenomenal laws * of nature 



* I have used the term phenomenal laws to designate a class of laws of nature which are empirical in their 

 character, inasmuch as they are obviously not ultimate, although their derivation has not been discovered, but 

 which are more universal than those to which the term empirical is commonly applied. 



VOL. V. NEW SERIES. 50 



