166 Mr. Prideaux on the Atomic Weight 



microscope ; and if stirred and viewed by a bright sun, as al- 

 ready described, it will appear evidently filled with innumer- 

 able small linear bodies, writhing and twisting about with ex- 

 treme activity." 



Similar bodies, and equally in motion, were obtained from 

 animal and vegetable tissues, from vegetable mould, from sand- 

 stone after being made red hot, from coal, ashes, and other 

 inorganic bodies. 



I believe that in thus stating the manner in which Mr. By- 

 water's experiments were conducted, I have enabled micro- 

 scopical observers to judge of the extent and kind of optical 

 illusion to which he was liable, and of which he does not seem 

 to have been aware. I have only to add, that it is not here 

 a question of priority ; for if his observations are to be de- 

 pended on, mine must be entirely set aside. 

 July 28, 1829. 



XXV. On the Atomic Weight of Oxalic Acid a7id of Mercury. 

 By Mr. John Prideaux. 



To the Editors of the Philosophical Magazine and Annals. 

 Gentlemen, 

 T N composing a scale of equivalents, now in course of publi- 

 cation, — more extensive, and designed to be more practical, 

 than the one now in use, — I had occasion to examine the atomic 

 weight of mercury, which I fancied Dr, Thomson had doubled; 

 and of oxalic acid in crystals, wherein Dr. Prout having found 

 but three atoms of water, while Dr. Thomson had found four, 

 the latter suggested the probability of more than one variety 

 existing. Being accustomed to meet with two varieties of these 

 crystals, one firm and transparent prisms, the other acicular, 

 friable, and with the aspect of quadroxalate of potash ; and 

 happening to possess some of each, I thought they might verify 

 this suggestion. 



1st. — 18 grains of the friable crystals were dissolved in dis- 

 tilled water, and gi-adually mixed with a solution of 36 grains 

 of dry transparent crystals of carbonate of soda. The mix- 

 ture, boiled to drive off the carbonic acid, reddened litmus 

 paper; and required for neutralization 5" 15 grains of carbo- 

 nate of soda. A minute portion more gave signs of alkali. 



2nd. — 9 grains of the same acid were neutralized with am- 

 monia, and 6-25 grains of carbonate of lime, in clean rhombic 

 crystals, were placed in a test tube with a little distilled water, 

 adding muriatic acid, three drops at a time, until with the aid 

 of heat it was dissolved, when it was washed out into the seg- 

 ment of a Florence Hask and slowly evaporated to dryness. 



Being 



