Eobeetson. — On certain Maxima and Minima. 475 



The odd members behave regularly, showing a maximum 

 at the C 5 amide, and then the values fall to a minimum. 

 This is the only example of two changes of this nature that 

 I have been able to find. The melting-points of the amides 

 with an even number of carbon atoms show a more or less 

 irregular nature. 



The anilides also show a somewhat similar behaviour, but 

 in this case it is the minimum which is reached in the G 5 

 compound. 



(b.) Heats of Formation of the Oxalic Acids : The fol- 

 lowing data are due to Stohmann, Kleber, and Langbeim : — * 



Acid. 

 Oxalic 

 Malonic 

 Succinic 

 Glutaric 

 Adipic 

 Pimelic 

 Suberic 

 Azelaic 

 Sebacic 



The values for the heat of formation increase with the 

 molecular weight just as the boiling-points do. But on 

 taking differences and separating the values thus obtained 

 alternately into two sections we find that both series reach 

 a minimum in the neighbourhood of pimelic acid. This 

 is the only instance in which the two minima occur in 

 neighbouring members ; usually there is a wide difference. 



General Conclusions. 



As regards the position of the maximum or minimum in 

 the series, we must first consider the results in division A. 

 In only one case does the change occur well up the series ; 



* J. pr. Chem., 40, 202. 



