1839.] 



On Chemical Tests, 



323 



c. Neither carbonate nor phosphate of soda; phosphate of potash ; 

 tartaric acid ; oxalic acid ; chloride of platinum; hydrofluosilicic acid, 

 nor sulphate of alumina produces any precipitate in solutions of lithia. 

 If phosphate of soda and then ammonia be added to a solution of 

 lithia a precipitate is produced but not instantly. 



d. The solutions of the salts of lithia act upon reddened litmus 

 paper in the same manner as the corresponding salts of potash and soda, 

 see 98 c: and 110 d. 



77. LITMUS, the solution and tincture of litmus, and litmus paper all 

 act in the same manner, namehj, from blue, their natural colour they turn red 

 on the application of an acid. See 73, for exceptions to this general 

 rule, also b in this article. 



a. Fixed acids turn litmus permanently red ; volatile acids produce 

 a transient red which disappears on the application of heat, or when 

 the paper gets dry. Carbonic acid and sulphuretted hydrogen in wa- 

 ter turn litmus a transient red, before, but not after boiling. 



b. The salts of silver and manganese have no effect on litmus pa- 

 per. The salts of nickel and cobalt affect it slightly, but solutions of 

 the neutral salts of all the following substance turn it red :— ? 



Antimony, 



Iron, 



Alumina, 



Lead, , 



Bismuth, 



Mercury, 



Cadmium, 



Platinum, the oxide, not the chlorid 



Cerium, 



Tin, 



Copper, 



Yttria, 



Glucina, 



Zinc, 



Gold, 



Zirconia. 



c. Solution of boracic acid changes blue litmus to red or reddish ; 

 and renders turmeric paper brown. 



78. LITMUS reddened. Litmus or litmus paper reddened By diluted 

 vinegar, or by any very weak acid becomes a test for alkalies. The blue 

 litmus is a test for acids. Suppose a piece of blue litmus paper to be 

 dipped into a weak acid, it will turn red ; if it then be dipped into an 

 alkaline solution it will turn blue, and regain its natural colour. This 

 effect will be produced as often as it is dipped alternately into an acid 

 or alkaline solution of equivalent strength. See 98, c. 



