[ 187 ] 



XXV. Chemical Notices from Foreign Journals. 

 By E. Atkinson, Ph.D., F.C.S. 



[Continued from p. 62.] 



IN 1860 Stas published an important memoir on the deter- 

 mination of the atomic weights of some of the elements, a brief 

 abstract of which appeared in this Journal*. From his experi- 

 ments he drew the conclusion that Prout's law is invalid, — that 

 is, that the atomic weights of the elements are not multiples by 

 a whole number of a fundamental unit — an idea which is at the 

 basis of the hypothesis of the identity of matter. The conclu- 

 sions derived by Stas from his experiments were contested by 

 Marignacf, who upheld the validity of Prout's law. 



Since 1860 Stas has been engaged in continuing his investi- 

 gations, and has recently published the results in a large quarto 

 volume of 800 pages, illustrated by numerous engravings of the 

 apparatus he used. Besides making fresh determinations, Stas 

 has incidentally investigated the question whether the circum- 

 stances under which a body is formed have any influence on its 

 composition ; and he has found that, in the case of chloride of 

 ammonium, neither different modes of preparation nor differ- 

 ences in temperature and pressure at the time of its formation 

 have the slightest influence. 



He has also treated the question of the invariability of the 

 relations in weight of the elements forming chemical compounds. 

 Thus, if there are two bodies, a binary compound A B and a 

 ternary compound ABC, which have the two elements in com- 

 mon A and B, is the ratio of A to B in each case the same ? 

 For instance, in iodide of silver and in iodate of silver, is the 

 ratio of iodine to silver in each case the same ? 



The following abstract of Stas's researches is taken from the 

 Zeitschrift der Chemie } and will, though inadequately, give an idea 

 of their value. From the scale on which they were undertaken, 

 the knowledge and judgment displayed in devising and selecting 

 the methods, and the skill and conscieutious care with which all 

 possible sources of error are either corrected or allowed for, these 

 researches are certainly without example in this kind of inves- 

 tigation. 



I. 



The research is divided into three parts, in the first of which 

 the author treats of the constancy of composition of chemical 

 substances. To the preparation of the materials used he devoted 

 the greatest possible care. 



- *» Phil. Mag. S. 4. vol. xxii. p. 138. f Ibid. p. 142. 



