[ 74 ] 



depofite an ochry fediment. The alkali, unit- 

 ing with the vitriolic acid, depofites the iron, 

 which unites with a portion of pure air, forming 

 a calx of iron. 



e. On adding a folution of foap, the fame 

 appearances take place as defcribed (page 72, d.) 



f. On adding a folution of liver of fulphur, 

 a black precipitate will immediately appear : if 

 to this black precipitate a few drops of vitriolic 

 acid be added, it will be perfectly rediffolved as 

 before. 



g. If water be added, impregnated with 

 hepatic air, the fame effect will be produced. 



B. h. The nature of the acid may be more 

 perfectly determined, by adding a folution of 

 muriated ponderous earth, when white clouds 

 will inftantly be formed. The ponderous earth, 

 uniting with the vitriolic acid, forms barofele- 

 nite, which is precipitated, while the iron, com- 

 bining with the muriatic acid* remains diffolved 

 in the water ; for, upon adding the Pruffian lixi- 

 vium, or tin&ure of galls, the blue or purple 

 precipitates will appear, 



i. By adding a folution of nitre of mercury, 

 a beautiful yellow precipitate will be obtained. 

 The vitriolic acid uniting with the mercury- 

 forms turpeth mineral, while the nitrous acid, 

 uniting with the iron, remains diffolved in the 

 water, as may be known by adding the tin6tur<g. 

 of galls, or Pruffian lixivium. 



VITRI- 



