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bertholet’s eudiometer.

is sent up reaches the phosphorus, a combustion will take placeand the mercury will rise again. The combustion continues tillthe end of the operation; but for the greater exactness, Mr.Seguin directs the residuum to be heated strongly. When cold,it is introduced into a small vessel, whose capacity has been as-certained at the same time as that of the preceding. The diffe-rence of the two volumes gives the quantity of the oxigen gascontained in the air subjected to examination.

Remark. ..The objection to which this eudiometer is liablewill be noticed in the next, which is said to be an improvementof this.

6. BERTHOLET’s EUDIOMETER.

Instead of the rapid combustion of phosphorus, Bertholet hassubstituted its spontaneous combustion which absorbs the oxigenof atmospheric air completely, and when the quantity of air ope-rated on is small, the process is accomplished in a short time.

Bertholet's apparatus consists of a narrow graduated glass tube,containing the air to be examined, into which is introduced acylinder or stick of phosphorus supported upon a glass rod, whilethe tube stands inverted in water. The phosphorus should benearly as long as the tube. Immediately after the introductionof the phosphorus, white vapours are formed which fill the tube,these vapours gradually descend and become absorbed by thewater. When no more white vapours appear, the process is atan end, for all the oxigen gas which was present in the confinedquantity of air, has united with the phosphorus; the residuum isthe quantity of nitrogen of the air submitted to examination.

Remark. ..This eudiometer though excellent of the kind, isnevertheless not absolutely to be depended upon ; for as soonas the absorption of oxigen is completed, the nitrogen gas exer-cises an action upon the phosphorus and thus its bulk becomesincreased. It has been ascertained that the volume of nitrogengas is increased to part; consequently the bulk of the re-