334 NOTES ON TRILINEARS. 



and efflorescing in the air. No salt with "Werther's formula could 

 be obtained. 



On the Oxidation of Alkaline Arsenites. 

 Fresenius found that a solution of arsenite of potassium became 

 rapidly oxidised, forming an arsenate, a change which would, of 

 course, render it useless in volumetric experiments. On making 

 some experiments on the subject, I was unable to discern the cir- 

 cumstances under which the strong oxidation described by Fresenius 

 took place, as in my experiments less than one per cent, of arsenious 

 acid was oxidised after a period of twelve months. Lately, a solution 

 has come under my notice, in which at least twenty per cent, of the 

 arsenious had become arsenic acid. The solution was very strong, 

 and had deposited some of the arsenite as warty crystals. For 

 accurate volumetric experiments it would, therefore, be advisable ta 

 examine the alkaline arsenite from time to time. 



NOTES ON TEILINEAES. 



In Vol. IX., No, 52, of this Journal, were given some illustra- 

 tions of the use in trilinear coordinates of the equation to a line 

 under the form 



a-/ P - 9 y -fi 



I 



r, 



where (a, jB, y) are the current coordinates, (/, g, h) the coordinates 

 of some assumed point in the line, and r is the distance between 

 these points. 



The quantities I, m, n, being the sines of the angles between the 

 line and the sides of the triangle of reference, when one of them is 

 assigned the other two are determinate, and there must, therefore,^ 

 exist two relations between the three. One such relation is well 

 known to be 



al + hm + en ■= 0, 



where a, h, c, are the sides of the triangle of reference. Another 

 can be found as follows : — 



