Eudiemdric Obfervations. ny 



When the operation is fininied, this cloud is not longer to be perceived. It is luminous in 

 the dark, and as foon as it has difappeared, the abforption no longer proceeds even during 

 the fpace of feveral days. So that by this means a certain indication of the conclufion 

 of the experiment is obtained; and if it be made in a narrow tube, it requires no more 

 than two hours at the temperature I have mentioned *. 



The air with which the experiment was made, is meafured in a graduated tube, and when 

 the operation is concluded, the remaining gas is meafured in the fame tube with the ufual 

 precautions that the changes of temperature and preflure of the atmofphere require. 



The diminution obtained by phofphorus is found to be confiderably lefs than that ob- 

 tained by the fulphuret ; but the proportions are always the fame, becaufe the phofphorus 

 being diiTolved in azote, as I have proved, takes the gafeous form, as do all fubftances 

 which are diflblved in a gas. The volume of azote is thus augmented, and feveral 

 experiments have (hewn that this increafe is about a fortieth part. 



The difference that appears in the diminution between the phofphorus and the ful- 

 phuret cannot be caufed 'by the one feparating the oxigen lefs exaftly than the other ; for 

 the phofphorus a£ls fo ftrongly on oxigen when it is diflblved in azote, that it is fufficient 

 to pafs the phofphorated azote through water to render it luminous, and make it burn 

 with the oxigen it meets. 



It appears to me that fulphurated hydrogen, which is foluble in the azote, is capable of 

 precipitating moft of the phofphorus. For if the phofphorated azote be placed over the 

 fulphuret of alkali, its bulk is dirainifhed ; but the total diminution is not fo great as if the 

 air had been firfl placed on the fulphuret. The phofphorated azote, which has been thus 

 diminifhed by fulphuret, is no longer capable of being. rendered luminous by coming in 

 conta£l with oxigen gas. 



If phofphorus be introduced into the azote which is in contact with the fulphuret, it 

 produces no fenfible effeft -, but if the azote be wafhed by being pafTed through clear 

 water, it will be fufhcient to render the water immediately luminous, fo that the water 

 retains the greateft part of the fulphurated hydrogen, and gives a very fmall quantity of 

 oxigen to the azote gas, which by this operation is made capable of dilFolving phofphorus, 

 and of acting on the fmalleft quantity of oxigen gas. 



I have obferved, that the azote which has been expofed with the fulphuret, does not 

 apparently lofe or acquire any thing in its bulk, when it has been pafied through the water, 

 and the combuftion that takes place when phofphorus is introduced is fo fmail, that it cati 

 fcarcely be appreciated. 



I, therefore, conclude, from all the preceding fa£ls, that the method with phofphorus 

 is at the fame time the moft convenient and the moft accurate, and that the time is not 



* Tliefe experiments were repeated at a temperature from fix to ten degrees of the thermometer centi- 

 grade, and it only required fix or eight hours for the operation to be concluded. M. Humboldt mentions 

 experiments wliich has lafted feveral days, after which the gas ftill reddened with the nitrous gas. He 

 muft have tried very different methods to have produced fo great a difference in the refults. 

 • Vol. IV. — August 1800. Ff inconvenient; 



