24 Mr. W. Sutherland on the Fundamental 



passing from the value for -JSr to that for -JBa the increase is 

 only I/O, but the value for ^Ba is quite uncertain. The 

 differences for the three members of the Li family are not 

 regular, being *7 from Li to Na, and 2*7 from Na to K, the 

 latter being close to the values 2*9 and 2*6 in the Mg family. 

 Both in the Li and the Mg families (R) increases with 

 increasing atomic mass ; but in the Cu and Ag family we find 

 a diminution of (R) in passing from Cu to Ag, the decrease 

 in (R)/3'8 being 3'0, which is close to the 2*9, 2'6, and 2'7 

 already found in the other families. It is interesting to find 

 on passing from Zn to Cd that the value of (R) is stationary, 

 for like Cu and Ag these two metals form a subfamily, and 

 might be expected like them to have (R) diminishing with 

 increasing atomic mass, but they are much more closely 

 related to their main Mg family, which might be expected to 

 give increasing (R) with increasing atomic mass ; the two 

 tendencies appear to neutralize one another and leave (R) 

 stationary. More data are required before the law regulating 

 (R) can become clear, and these are specially desirable for 

 the compounds of the rarer metals of the Li and Be families, 

 that is for the haloid compounds of Rb and Cs, and of Be and 

 Ba. BeketofF has made determinations for the compounds of 

 Rb in solution, but I have not seen any determinations of the 

 heat of solution of RbCl, RbBr, and Rbl ; Petersen has also 

 made some determinations for Be, but not complete. It can 

 be seen that the most important thermochemical experimental 

 work for immediate requirements is the determination of 

 such hitherto undetermined data as will enable a table to be 

 drawn up showing the heats of formation of the haloid com- 

 pounds of all the metals, reagents and products being in the 

 gaseous state. 



I have not discussed the available data for the heat of for- 

 mation of the nitrates, sulphates, and carbonates of the metals, 

 because it seems desirable that the simpler problem of binary 

 compounds should be carried further towards solution before 

 the more complex one is handled. A few data for the fluorides 

 are available for discussion, for Guntz (Compt. Rend, xcvii.) 

 has given values for the heat evolved when gaseous HF acts 

 upon the solid hydrates to produce solid fluorides and solid 

 H 2 0. Let R be an equivalent of any metal, and A the 

 quantity of heat found by Guntz, then we have the thermo- 

 chemical equation 



ROH solid + HF gas = RF solid + H 2 solid + A. 



From Thomsen's data we can get the values of B in the 

 equation 



R solid + + H = ROH solid + B, 



