ON PRUSSIAN RLFK 



precipitating all the metallic substances ; and I shall con- 

 sequently call it the precipitating liquor. 



SECTION XII. 



(a) The colouring matter has no sensible action, either 

 upon metals or upon metallic solutions, except upon nitrated 

 silver, which is precipitated in the form of a white powder ; 

 nitrated mercury, which is precipitated in the form of a black 

 powder ; arid the solution of iron in aerial acid, which is 

 precipitated first of a sea-green colour, but at last changes to 

 a blue colour. The other metallic solutions undergo no 

 change. (&) This matter has a more sensible action upon the 

 calxes and metallic precipitates. All the calxes, however, are 

 not attacked ; for it produces no effect upon the calxes of 

 platinum, tin, lead, bismuth, iron, manganese, and antimony ; 

 as little does it act upon the acids of inolybditna and of 

 arsenic. The following are the phenomena which it presents 

 with the other metallic calxes : -Gold, precipitated by aerated 

 alkali, becomes white. From silver, precipitated by the same 

 alkalies, it disengages the aerial acid with a slight effervescence, 

 but the calx preserves its white colour. It dissolves the 

 calx of quicksilver, and yields crystals by means of a gentle 

 evaporation. The calx of copper, precipitated by aerated 

 alkali, effervesces, and assumes a faint citron colour. Calx 

 of iron, precipitated from its solution in the vitriolic acid by 

 the same alkali, effervesces, and assumes a dark blue colour. 

 Precipitated cobalt shows some signs of an effervescence, and 

 changes into a yellowish brown colour. Calx of manganese, 

 precipitated from its solution by aerated alkali, is not 

 attacked. 



