Additional Notes.. 49 J 



modifications and improvements by Falconiir, Cavendish, 

 and Van Humboldt, but is still liable to considerable ano- 

 maly and inaccuracy in its indications. 



2. The second kind of Eudiometer was proposed by Vol- 

 TA. His method was to mix given proportions of the air 

 to be examined, and hijdrogen gas, in a graduated glass tube ; 

 to fire the mixture by an electric spark ; and to judge of the 

 purity of the air by the bulk of the residuum. But this fur- 

 nishes a measure even less to be depended on than the pre- 

 ceding. 



3. ScHEELE was the inventor of* the third kind of Eudio- 

 meter. It is merely a graduated glass vessel, containing a 

 given quantity of air, exposed to newly prepared liquid alka- 

 line or earthy sulphurets, or to a mixture of iron-filings and 

 sulphur, formed into a paste with water. These substance* 

 absorb the whole of the oxygen of the air, which converts a 

 portion of the sulphur into an acid. The oxygen contained 

 in the air thus examined is judged of by the diminution of 

 bulk which the air has undergone. This method is simple, 

 and as accurate as any other. The only objection to which it 

 is liable is the slowness of the process. But this objection has 

 been removed by M. De Marti, who has brought the eu- 

 diometer of ScHEELE to a great degree of accuracy, by im- 

 proving the apparatus, and, instead of iron-filings and sulphur, 

 using the hydrogenated sulphurets only. 



GuYTON-MoRVEAU employs sulphuret of poi^ash, and 

 measures the proportion of oxygen present by the quantity ab- 

 sorbed by the sulphuret. 



4. In the fourth kind of Eudiometer, the abstraction of 

 the oxygen of air is accomplished by means of phosphorus. 

 This eudiometer was first proposed by Achard. It was con- 

 siderably improved by Reboul, Seguin, Lavoisier, and, 

 above all, by Berthollet, who has rendered it equal iu 

 simplicity with the eudiometer of De Marti, and scarcely 

 inferior to it in precision. 



5. The fifth Eudiometer has been lately proposed by Mr. 

 Davy. In this the substance used to absorb the oxygen 

 from the air is a solution of sulphat or muriat of iron in wa- 

 ter, and impregnated with nitrous gas. This eudiometer ij 

 simple, and its indications nearly, if not quite, as accurate as 

 tliose of the two last mentioned. — Thompson'^- Chcniisiri/. 



