BORON. RAMSAY. 145 



constant and equal to the standard values, we shall obtain 

 0.58 020, which is "99 high." 



In fact, we might even apply this same reaction as a test 

 for the value of oxygen. Supposing O = 16.1 we shall 



obtain 



2Na Cl : Na2 O Bo* = 117 : 202.7 = 0.57 721 

 which value is "200 low" as compared to 0.57 921 found for 

 all standard values, including O = 16 exactly. 



But if a rise of o.i in the atomic weight of oxygen, 

 O = 16, causes a change of the atomic ratio of " 200 low," 

 it is evident, that a lowering of each single unit in the fifth 

 place of the atomic ratio will correspond to a rise of only 

 >^oo of o.i in the atomic weight of oxygen, that is an 

 amount of only 0.0005 rising. 



In general, it will facilitate the handling of these minute 

 changes, if we will observe that " change high " corresponds 

 to same sign, ' ' change low " to opposite signs of departure 

 and ratio. 



Accordingly, the reaction practiced by Ramsay and 

 Aston permits every one of the four elements to be tested, 

 as to the exact true atomic weight, provided we assume the 

 other tJiree constant or fixed, at their standard values for the 

 time being. 



The rates at which these variations take place, in the 

 fifth decimal of the ratio for an increase of one tenth unit 

 (o.i) of the atomic weight of the one element specified is 

 given in the following table, together with its inverse calcu- 

 lated as shown above. 



Change of atomic ratio, per o.i rise in atomic weight; and 



Change in atomic -weight, per rise of one unit in fifth 

 place of atomic ratio. 



Change of : Atomic Ratio. Atomic Weight. 



Boron, 115 low. o.oo 087 low. 



Sodium, 41 high. o.oo 244 high. 



Chlorine, 99 high. o.oo 101 high. 



Oxygen, 200 low. o.oo 050 low. 



To readily follow the sign (high or low) it suffices to 

 observe, whether a rise of o.i causes high or low, i. e. same 

 or opposite change. 



