320 



On Chemical Tests 



lead ought to be entirely soluble in water : any insoluble matter may be 

 regarded as an impurity. 



72. LIME is detected by oxalate of ammonia ; see 15 b, and by sul- 

 phuric acid, but the latter will not discover lime if it is held in very 

 dilute solution, see 15,35,44. 



a. A considerable number of the salts of lime are insoluble in water. 

 Some of those that are soluble cannot be easily crystallized. When a 

 salt of lime is insoluble in water if it be boiled for some time in a solu- 

 tion of carbonate of potash, a white powder remains which is soluble in 

 nitric acid with effervescence, and which possesses all the properties of, 

 and is in fact carbonate of lime. 



b. To distinguish precipitated sulphate of lime from the sulphate of 

 barytes, or of strontia, wash it well, and boil it in a considerable quan- 

 tity of water; filter, and divide into two portions; to one, add muriate 

 of barytes, to the other oxalate of ammonia. If a white precipitate be 

 produced in both cases, and the precipitate by the muriate of baryta be 

 insoluble in muriatic acid, then the base of the sulphate is lime. The 

 sulphate of baryta is insoluble in water ; the sulphate of strontia is not 

 quite insoluble, but very nearly so. 



c. Salts of lime are distinguished from alkaline salts by giving white 

 precipitates with carbonate of potash, and if not too dilute with sulphu- 

 ric acid. 



d. Lime may be distinguished from baryta by its giving no precipi- 

 tate with hydrofluoric acid; and when in very dilute solution, by its 

 giving no precipitate with sulphuric acid. Baryta is acted on by both 

 those tests. 



e. Lime may be distinguished from strontia by sulphuric acid, but the 

 lime must be in weak solution. Strontian gives a white precipitate with 

 sulphuric acid and acts more rapidly on adding ammonia, but if the solu- 

 tion of strontian be very dilute the precipitate does not take place im- 

 mediately. The same method of discrimination may be followed with 

 respect to barytes. Sulphuric acid detects both strontia and barytes in 

 much weaker solutions than it detects lime, see 79 d. Lime may be 

 further distinguished from barytes and strontia thus : nitrate of lime 

 crystallizes in prisms, is very deliquescent, and is soluble in alcohol. 

 The nitrates of barytes and strontian crystallize in octahedrons, or seg- 

 ments of octahedrons ; are not deliquescent, and do not dissolve in pure 

 alcohol, see 44 c. 



f. Lime is always found in nature combined with an acid, see 39£ c. 



