146 Scientific "Notices-— -Chimistr^, |^^k 



the soda penetrates it, and do not give a limpid mixture when 

 they are melted on a leaf of platina. With twice its weight of 

 carbonate of lime, it fuses at a red heat, without however 

 attacking the platina, as lithia ordinarily does ; but if soriie 

 drops of water are added to it, and afterwards evaporated, the 

 platina becomes yellow all round when the mass is heated anew. 

 — (Edin. Jour, of Science.) 



2. Prof. Berzelius's Experiments on the Orange Gas produced 

 from a Mixture of Fluor Spar and Chromate of Lead. 



As the English and French journals have already given an 

 account of Prof. Berzehus's experiments on the different combi- 

 nations of the fluoric acid which have facilitated the reduction 

 of silicium, zirconium, and tantalum, we shall not at present 

 enter on the subject. 



A German chemist, M. Unverdorben, has published some 

 experiments on the fluoric acid, the most curious of which was 

 that in which, after mixing together fluor spar and chromate of 

 lead, he distilled them in a leaden retort, with fuming or anhy- 

 drous sulphuric acid. From this there resulted a gas, which 

 could not be collected, because it destroyed the glass. This gas 

 gave a very thick yellow or red smoke. It was readily absorbed 

 in water, which was then found to contain a mixture of chromic 

 and fluoric acids. When it came in contact with air, the gas 

 deposited small red crystals, which were those of chromic acid. 



Prof. Berzelius repeated these experiments of M. Unverdorben, 

 and he found that the experiment succeeded equally well with 

 common concentrated sulphuric acid. He collected the gas in 

 glass flasks covered with melted resin, and filled with mercury. 

 The gas had a red colour. It gradually attacks the resin, depo- 

 sits chromic acid in its mass, and penetrates even to the glass, 

 which it decomposes without change of volume, the chrome 

 being replaced by silicium. Aramoniacal gas introduced into it 

 burns with explosion. Water dissolves it, and yields an orange-* 

 coloured fluid, which, evaporated to dryness in a platina dish, 

 leaves as a residue pure chromic acid. The fluoric acid volati- 

 lizes entirely. This method is at present the only one which 

 gives chromic acid perfectly pure. 



If the gas is received in a platina vessel of some depth, whose 

 sides have been slightly wetted, and into the bottom of which the 

 gas has been made to descend, the water begins to absorb the 

 gas, but, by and bye, crystals of a fine red colour are seen to 

 form themselves round the opening of the metallic tube which 

 conveys the gas, and, in a short time, the vessel is filled with a 

 red snow, consisting of crystals of chromic acid. The fluoric 

 acid dissipates itself in vapour, and absorbs entirely the water 

 added at the beginning of the experiment. These crystals have 

 this curious property, that, when they are heated to redaess in a 



