160 On Phosphoric Acid and Phosphorus, 



Tn the phosphorization of copper there is only a part of 

 the anhnal glass decomposed, because a quantity of char- 

 coal necessary to phosphorize the whole acid has not been 

 employed : but it is necessary that this should be the case 

 in order that the vitreous scoria should be sufficiently fluid 

 for the phosphorus to be disengaged and to collect itself 

 readily. 



The dark red enamel which is formed in this experiment 

 may be employed with advantage for porcelain and enamels, 

 as this red does not alter in the fire. 



Copper can combine with phosphorus only in the dry 

 wav. If a cylinder of phosphorus be put into a solution of 

 nitrate of copper diluted with four or five thousand parts of 

 water, copper under the metallic form will be found at the 

 end of eight days crystallized and ductile, forming a case to 

 the cylinder of phosphorus. 



XXVIII. On Phosphoric Acid and Phosphoiiis. By 

 Jos. Hume, Esq. 



To Mr. Tilloch. 



DEAR SIR, 



jfxT the request of a medical friend of mine, I lately made 

 some experiments with a view to form a comparative esti- 

 mate between healthy urine and some of a peculiar morbid 

 nature. 



In this analysis, amongst other observations which oc- 

 curred, I f«und that acetite of lead is by no means to be 

 depended on as the best test for phosphoric acid ; that it is 

 liable to induce error; and in many instances where it has 

 been trusted to ascertain the quantity of the acid, the accu- 

 racy of the results may be suspected, especially where the 

 subject did not consist of a simple phosphate. 



If my professional avocations permit, I shall endeavour 

 to extend many of these remarks, and fit them, under some 

 arranscemcnt, for a future number of the Philosophical Ma- 

 gazine. It may be proper, however, to acquaint you, that 

 the substitutes I employed in lieu of acetite of lead, were 

 nitrates of lead, of barytes, or of zinc; and some other 

 metallic salts which need not be najiied. 



In point of ceconomy and efficacy nitrate of lead is vastly 

 superior to the acetite for the .most exact and complete se- 

 paration of phosphoric acid : hence in all cases whatever 

 it ought to be universally preferred in the preparation of 

 phosphorus. 



With 



