422 M. BECQUEREL ON CHEMICAL DECOMPOSITION AND 



suppose that the tube contains it in excess : at first protoxide is pro- 

 duced and crystallized ; the solution gradually loses its colour ; then be- 

 comes colourless, and crystals of nitrate of ammonia are seen on the in- 

 terior surface of the tube. The liquor now contains nothing but the 

 saturated solution of this salt and some traces of copper. Sometimes it 

 takes a year or more to obtain this last result, which depends on the 

 quantity of deutoxide employed. All this is effected without any con- 

 tact with the air, since the tube is hermetically sealed, and the forma- 

 tion of the ammonia must have been owing to the hydrogen of the 

 water and the azote of the nitric acid. 



When the quantity of the deutoxide is very small, the effect is as fol- 

 lows : the i^rotoxide crystals are formed equally on the plate of copper ; 

 but by Httle and little, they lose some of their brilliancy, and experience 

 at last a discoloration which stops at a certain point. The solution re- 

 mains always coloured. The experiment is then terminated, and time 

 produces no change in tiie solution. 



In order to explain the facts just mentioned, and to reascend to the 

 cause of the electric phsenomena by which they have been produced, 

 we have found it necessary to analyse the octahedral crystals and the 

 substance that replaces the deutoxide of the same metal. The change 

 which the deutoxide undergoes is the only thing that can throw a light 

 on the origin of the electric effects. 



Those crystals possess the following properties : their powder is red : 

 it is soluble in ammonia or in hydrochloric acid without colouring either. 

 The latter solution is made turbid by the Avater, and receives a blue tinge 

 from ammonia. These characters indicate that the crystals really are 

 protoxide of copper. 



Analysis of the Substance ivhich replaces the Deutoxide of Copper 

 in the Crystallization of the Protoxide. 



We took tMO grammes of this substance. After having well washed 

 and dried it, we proceeded to operate on it immediately by means of car- 

 bonate of potash. The filtrated liquor was gradually saturated with 

 sulphuric acid, until there was no longer any alkaline reaction. Hav- 

 ing now condensed the solution by evaporation and produced crystal- 

 lization, we obtained l^'-O of nitrate of potash besides the mother-water 

 which we neglected. 



The insoluble salt which remained on the strainer was carljonate of 

 copper, which being dried and weighed amounted to W'6. Now one 

 gramme of nitrate of potash, if we admit that an atom of this salt includes 

 two atcmis of acid and one atom of base, will contain 0^'5 of acid and 

 0*45 of potash. 



In like manner the carbonate of copper, being formed of an atom of 

 deutoxide of copper and an atom of carbonic acid, gives 1*2 of oxide 

 and 0*4 of carbonic acid. 



