168 Intelligence and Miscellaneous Articles. 



determining their strength. From experiments on hollow pillars of 

 cast-iron, formulae representing the strength of such pillars are, in 

 like manner, deduced. 



The strength of pillars of wrought iron and of timber, in relation 

 to their dimensions, is made the subject of another series of experi- 

 ments. The result for wrought iron is, that the strength varies in- 

 versely as the square of the length of the pillar, and directly as the 

 power 3"75 of its diameter, the latter being nearly identical with the 

 result obtained for cast iron ; while in timber, the strength varies 

 nearly as the fourth power of the side of the square forming the sec- 

 tion of the pillar. In like manner, the power of cast-iron pillars to 

 resist long-continued pressure, and the relative strengths of long pil- 

 lars of cast iron, wrought iron, steel and timber, are determined. 



The inquiry which constitutes the subject of this paper is not, 

 however, the first of the kind in which Mr. Hodgkinson has been 

 engaged ; several series of experiments and papers on the strength 

 of iron, in various forms, have been published by him at different 

 times ; and their accuracy has established his claim to our confi- 

 dence on the present occasion. 

 [The remainder of the Anniversary Proceedings will be given next month.] 



XXVI. Intelligence and Miscellaneous Articles. 



PREPARATION AND COMPOSITION OF SEBACIC ACID. BY 

 J. REDTENBACHER. 



MTHENARD prepared this acid by treating the products of 

 • the distillation of most fatty bodies with boiling water ; as 

 the solution cools, foliated crystals of the acid separate ; these are 

 purified by adding acetate of lead to the aqueous solution, and by 

 decomposing the precipitate with hydrosulphuric acid. 



Berzelius prepared this acid by boiling the product of the distilla- 

 tion of fatty bodies with carbonate of lime diffused through a large 

 quantity of water, and decomposing the sebate of lime formed by 

 nitric acid. Berzelius supposed the acid thus produced to be benzoic 

 acid modified by some empyreumatic matter. 



MM. Dumas and Peligot gave the following as the composition of 

 hydrated sebacic acid : C" H'« O^ + H- O, the water being separable 

 by an equivalent of a metallic base ; with this the analysis of M. 

 Redtenbacher agrees. 



After relating various experiments on the preparation of this acid, 

 M. Redtenbacher observes, that the greater part of fatty bodies, both 

 of animal and vegetable origin, yield sebacic acid when they are 

 distilled, as ox-fat, hog's-lard, olive-oil, &c. Neither stearin nor 

 margaric acid, nor glycerin, when they are pure, yield the smallest 

 trace of sebacic acid by distillation : as fats and oils contain only 

 oleic acid besides the three compounds above named, it follows as a 

 necessary conclusion, that sebacic acid is produced from it by distil- 

 lation. 



"When oleic acid is distilled alone, the product, among other sub- 

 stances, contains a large portion of sebacic acid, the quantity of 



