1 50 M. Dcebereiner on the agency ofPlatina. 



dupois from the troy pound, and thence the weight lo be em- 

 ployed in determining the capacity of the gallon. 



As no balance exists, either at the Mint or at the Bank of 

 England, capable of weighing upwards of 230 pounds avoir- 

 dupois, I have given Mr. Bate the plan of a beam for this 

 purpose, of great simplicity, and which, I trust, will be more 

 accurate than any that has been hitherto made. This beam 

 is also to be finished by the 1st of February. 



The standards of linear measure have been prepared by 

 Mr. DoUond, and are now ready for my final adjustment. 



The Commissioners will perceive that no further difficulty 

 exists ; and should I receive the models from Mr. Bate by the 

 1st of February, according to his engagement, I trust I shall 

 be able speedily to complete their adjustment, and that they 

 will be ready for delivery in two or three weeks from that 

 period. 



York Gate, Regent's-park, HenRY KateR. 



]2thJan. 1825. 

 To the Commissioners of Weights and Measures. 

 Whitehall Treasury Chambers, Feb. 4, 1825. 



ON THE AGENCY OF PLATINA IN EFFECTING THE FORMATION 

 OF WATER. 



If in a tube closed at one end ammonia-muriate of platina 

 is heated till completely decomposed, or if a solution of platina 

 is treated with metallic zinc, part of the inside of this tube be- 

 comes covered with a thin coat of platina which adheres to it 

 rather strongly. If afterwards a mixture of hydrogen and 

 oxygen is made to pass under water, into this tube, the com- 

 bination of the two gases is slowly effected at a moderate tem- 

 perature. The phaenomenon also takes place when these 

 gases are put in contact with spongy platina moistened with 

 water or with alcohol. If we try to substitute liquid ammo- 

 nia or nitric acid for the water or alcohol, the gases no longer 

 act upon each other. M. Dcebereiner thinks that this dif- 

 feience of effects is to be asci'ibed to the water or alcohol 

 absorbing the gaseous mixture, and thus effecting immediate 

 contjict with the platina, whicli does not take place with the 

 ammonia or nitric acid. By using vessels covered inside with 

 platina, the hydrogen may be completely deprived of oxygen. 

 However, it succeeds still better by putting it in contact, in 

 very dry eudiometers, under mercury, with a porous ball form- 

 ed of clay and of platina newly calcined. M. Dcebereiner 

 describes a simple apparatus fit for determining with care the 

 formation of water by means of platina. 



At a little distance from the opening of a flask of tiie ca- 

 pacity 



