Influence of Atomic Weight. 381 



Ber. vii. p. 676, ix. p. 1188, x. pp. 848, 1871, xi. pp. 1109, 

 1142, 2017, 2128, xii. p. 119; Pogg. Ann. clx. p. 199) has 

 shown that when an element like silver and a series of its 

 compounds have volumes which stand exactly to one another 

 in simple relations, then they have equal volume-masses or 

 equal steres. Every volume may in fact be represented as a 

 simple multiple of a common volume-mass or stere. So that, 

 "In every solid compound the volume-measure or stere of one of 

 its elements determines all the oilier components, and causes 

 equal volume-measures to take up equal steres." In other words, 

 one of the elements of a compound impresses its own volume- 

 mass or stere on the whole compound, and becomes the con- 

 trolling element in a whole series of otherwise very different 

 compounds. Thus : — 



Calculated Observed 



volume. volume. 



Ag? = 2x5-14 = 10-28 =10'28 



AgjCl-J = 5x5*14 = 25-70 =25-70 



AgjBr} = 6x5-14= 30*84 =30-84 



AgflJ =8x5-14=41-12 =41-12 



In the above examples the number of atoms in a compound 

 is indicated in the usual way by a number placed to the right 

 and under side of a symbol, and the number of its steres by a 

 number at the right of the upper side. Here in these com- 

 pounds it is seen that silver is the predominating element ; 

 for it impresses its stere ( = 5-14) on all the other compounds. 

 By the use of this law Schroeder has endeavoured, with some 

 success, to determine the molecular weight of a solid body ; 

 for if substances combine only in whole volumes, then the 

 molecule of a body must contain the number of atoms which 

 are necessary for the components of the compound to fill 

 the space of the whole number of volume-units. He also 

 shows that in many compounds which are capable of existing 

 in more than one form, the difference in form depends on 

 which is the dominating element in the compound. Thus 

 black cinnabar is distinguished from the red by the fact that 

 in the former the mercury stere dominates, whilst in the latter 

 it is the sulphur stere. 



[To be continued.] 



