292 



On Chemical Tests. 



[Ocr. 



f. Tin is precipitated by nitric acid in the state, of pure oxide. 

 (j. Carbonic acid is liberated with effervescence by nitric acid, in the 

 same manner as by muriatic, or sulphuric acid. See lie, and 18 g. 



14- ACID nitric detected. If a solution contain nitric acid free or 

 in combination icith a base, it wffll not by itself dissolve gold leaf but on the 

 addition of muriatic acid the gold will be dissolved, nitro- muriatic acid being 

 formed. Morphia turns nitric acid of a beautiful orange red colour. Nitrate 

 salts deflagrate ivhen thrown on red-hot charcoal. Nitrates are also de- 

 tected by sulphuric acid, see 18 a. Strong sulphuric acid and copper 

 filings being put into a test tube with a nitrate salt, the acid will be 

 detected by the disengagement of orange-yellow vapours. 



a. Nitric acid should be as limpid as water and be kept in a dark 

 place to prevent its conversion into the nitrous kind. It may be adul- 

 terated with sulphuric, or muriatic acid, either of which may be detected 

 by the proper tests: see 40, and 108. 



b. Concentrated nitric acid has a specific gravity of 1500, but it is 

 seld om found so heavy. 



IS- ACID oxalic, detects lime producing a white precipitate of 

 oxalate of lime. See 35,44^72. See 35 for precautions in using the 

 test of oxalic acid for lime. Many of the metals are acted on by this 

 test ; see table of re-agents. If nitrate of silver be dropped into a 

 solution of oxalic acid, a white precipitate of oxalate of silver occurs, 

 which being collected on a filter, dried, and heated, first becomes brown 

 on the edges, then fulminates and is dispersed. 



a. Oxalic acid oxidizes lead, copper, iron, tin, bismuth, nickel, cobalt, 

 zinc and manganese. It also combines with alkalies, earths, and metal- 

 lic oxides and forms salts known by the name of oxalates. 



b. Oxalic acid is detected by muriate (or hydrochlorate) of lime, 

 producing a white precipitate of oxalate of lime, soluble in nitric acid; 

 which distinguishes it from sulphate of lime. On the other hand oxa- 

 late of lime is not soluble in a small quantity of muriatic acid, and this 

 distinguishes it from the tartrate, citrate, carbonate and phosphate of 

 lime. Sulphate of copper gives a faint bluish white or greenish white 

 precipitate of oxalate of copper, not soluble in a small, but soluble in a 

 large quantity of muriatic acid. Its insolubility upon adding a few 

 drops only of muriatic acid distinguishes it from the carbonate and 

 phosphate of copper. Nitrate of silver produces a detonating precipi- 

 tate as before mentioned, which is a good distinctive test of oxalic acid. 

 The citrate and tartrate of silver become brown and froth up, and the 



