made on a Mineral called Cer'ite. 1 95 



there is disengaged carbonic acid as well as nitrous gas 

 when nitric acid is employed. 



After ebullition of half an hour the action of the acids 

 appears to be exhausted, and there remains at the bottom 

 of the vessel a dust more or less coloured, which is the silex 

 ■contained in the mineral. 



When cerite is treated with eight or ten times its weight 

 of acid it is entirely decomposed by one operation, and 

 without the necessity of beginning a second time; yet it 

 is impossible by these means to obtain silex perfectly pure : 

 it always retains a certain quantity of metallic oxide. It is 

 only by fusing this earth with an alkali, and then combining 

 it with an acid, that it is possible to obtain it pure, and free 

 from all colouring matter: it generally forms about seven- 

 teen hundredths of the mineral. When the solutions of 

 this matter are evaporated to dryness and the residuum is 

 dissolved in water, there is formed a slia;ht white precipi- 

 tate, which appears to be a little silex which the acid held 

 in solution. 



Solutions of cerium are of a yellowish red colour, like 

 that of the oxide of iron at its maximum of oxygenation ; 

 but when cerium is little oxidated they are only of a rose 

 colour, similar to those of manganese and cobalt. 



These solutions, decomposed by ammonia, furnish a very 

 Voluminous precipitate, which has the appearance of alu- 

 mine mixed with oxide of iron, but which greatly differs 

 from it in its properties: when dried in a gentle heat this 

 precipitate is reduced to a granulated powder of a pale yel- 

 low colour, which becomes of a brick red by calcination. 

 The matter simply dried in the air redissolvcs readily in the 

 nitric and muriatic acids ; but the red oxide, that which 

 has not been calcined, is scarcely attacked, and does not 

 dissolve in muriatic acid without producing a very consi- 

 derable quantity of oxygenated muriatic acid. 



The nitric solution readily crystallizes : the silt which it 

 furnishes is soluble in alcohol : in regard to the muriatic 

 solution it is very difficult to obtain crystals: this salt when 

 dried is deliquescent. 



The nitric and muriatic solutions are decomposed by al- 

 kaline sulphates, phosphates, borates, oxalates, tartrites, 

 and carbonates : with sulphates there are formed yellow pre- 

 cipitates too soluble in water to be subjected to analytical 

 experiments : besides, a part of the iron oxidated to a max- 

 imum is precipitated at the same time. The pn-cipitate 

 formed by the borates is still more soluble in acids : that 

 produced by oxalates is attended with the ijiiconvenicnce of 

 j)<< 2 carrying 



