Intelligence and Miscellaneous Articles, 299 



again red or brown, but the greatest number are black. When it is 

 desired to fix these colours on the metal employed, it is sufficient to 

 withdraw it from the liquid as soon as the last colours begin to pre- 

 dominate, and to allow them to dry spontaneously in the air. 



By employing this simple and easy process, M. Bottiger succeeded 

 in fixing the most incompatible tints on the same metallic surface, 

 the aspect of which was, nevertheless, as soft as possible. — L Institute 

 September 1837. 



ON THE ACTION OF PROTOXIDE OF IRON ON PROTOXIDE 

 OF COPPER. 



M. Levol remarks that it is well known that the persalts of iron 

 are reduced to protosalts by the protochloride of copper ; whilst the 

 protosulphate of iron produces no such effiect with the salts of cop- 

 per, aj; least with the sulphate ; this fact being known, superior affi- 

 nity would, from analogy, be assigned to dioxide of copper over 

 protoxide of iron ; but the facts which M. Levol states prove that 

 this is not the case under all circumstances. 



If a mixture of sulphate of copper and protosulphate of iron be 

 dissolved in water, no chemical action, as is well known, takes place, 

 and the two oxides will remain mixed in solution, that is, under 

 the most favourable circumstances for reaction without any occur- 

 ring ; if, however, the oxides be precipitated by an alkali, the case 

 is no longer the same, and experiment shows that peroxide of iron 

 and dioxide of copper are obtained, instead of the oxides which ex- 

 isted in the two salts ; the iron, therefore, is peroxidized at the ex- 

 pense of the oxide of copper. 



The affinity of the two protoxides for sulphuric acid, the impossi- 

 bility of forming a sulphate of dioxide of copper, and even of the 

 existence of dioxide of copper in the presence of sulphuric acid, are 

 causes which unquestionably oppose the reaction of the oxides in 

 the two sulphates ; it appears, therefore, that half an equivalent of 

 oxygen, separated from the protoxide of copper, leaves it in the state 

 of dioxide ; and this, added to the equivalent of oxygen in the prot- 

 oxide of iron, converts that into sesqui- or peroxide. That this is 

 the case, is also shown by dissolving an equivalent of each sulphate 

 in water, and adding ammonia to the mixed solutions. When kept 

 from the contact of air, a colourless solution of ammoniuret of diox- 

 ide of copper will be formed, and peroxide of iron precipitated, con- 

 taining scarcely a trace of copper. 



If an equivalent and a half of sulphate of copper and one equi- 

 valent of sulphate of iron be similarly treated, peroxide of iron will 

 also be precipitated ; but blue ammoniuret of protoxide of copper 

 will also be formed ; when, on the contrary, the proportions were 

 reversed, a colourless solution was obtained which contained prot- 

 oxide, both of iron and copper ; and by exposure to the air it con- 

 sequently became of a blue colour, and precipitated peroxide of iron. 

 Potash produces the same precipitation of dioxide of copper and 

 peroxide of iron. 



