History of Air-Analysis 21 



sive use, be considerably increased in accuracy, and contribute materially 

 to our knowledge of the oxygen content of the air. 



Henry 1 analyzed atmospheric air frequently, using the Volta eudiom- 

 eter. He reports that he was unable to satisfy himself "whether it con- 

 tains 21 or 20 volumes of oxygen in 100, the proportion being mostly be- 

 tween these two extremes." 



Simultaneously with the Volta eudiometer, another method of air- 

 analysis was rapidly developed, which was also based upon the fundamen- 

 tal observations of Scheele with regard to the absorption of oxygen from 

 a confined volume of air by slowly or rapidly burning phosphorus. 

 Scheele's experiments have already been cited, but in the English trans- 

 lation of his book, 2 we find Richard Kirwan criticizing adversely Scheele's 

 results, maintaining that Lavoisier, when using the combustion of phos- 

 phorus, never found more than between one-fifth and one-sixth of oxygen 

 absorbed, while Scheele, it will be remembered, found a much larger 

 contraction in volume. Kirwan also pointed out that Fontana had made 

 experiments with phosphorus but found the diminution in volume much 

 less than that found by Scheele. Later Lavoisier 3 mentioned the fact that 

 when employing the combustion of phosphorus he found the quantity of 

 vital air contained in the atmosphere was about 27.5 parts in 100. 



Volta, in a letter to Priestley, 4 wrote in a general way of his experience 

 with "Bolognian phosphorus," showing that at the same time Scheele in 

 Sweden, Lavoisier in Paris, and Volta in Italy were using phosphorus to 

 absorb oxygen from the air. Rapidly burning phosphorus was also em- 

 ployed by Achard, 5 who described two eudiometers, one for nitric oxide 

 and one for rapidly burning phosphorus. 



Dissatisfied with the incomplete descriptions and development of the 

 earlier methods employing ignited phosphorus, Seguin 6 in his memoir on 

 eudiometry described accurately the methods used by Lavoisier and him- 

 self, but gave no results. It is noteworthy that after the ignition of the 

 phosphorus and the contraction in the volume of the air, they placed in the 

 jar a little caustic alkali to absorb the carbon dioxide and the phosphoric 

 acid. Seguin maintained that this method was very rapid and very exact. 



Simultaneously with his condemnation of the nitric-oxide eudiometer, 

 Berthollet advocated the use of slow-burning phosphorus. 7 In his ob- 

 servations on eudiometry, he criticized severely the nitric-oxide eudiometer 

 and the Volta hydrogen eudiometer, and stated that the use of alkaline 

 sulphide is too long a process and that hydrogen sulphide is present. 



1 Henry, Elements of experimental chemistry, London, 1829, 11th ed., I, p. 316. 



2 Scheele, Experiments on air and fire, London, 1780, p. 202. 



3 Lavoisier, Memoires de l'Academie des Sciences, 1782, p. 486; also in Oeuvres de 

 Lavoisier, 1862, 2, p. 503. 



4 Priestley, loc. cit., 1777, 3, p. 381. 



5 Achard, Nouveaux Memoire de l'Academie Royale des Sciences et Belles Lettres, 

 for the year 1778 (published 1780), p. 91. 



6 Seguin, Annales de Chimie, 1791, 9, p. 293. 



7 Berthollet, Memoires sur l'Egypt publics pendant les Campagnes du General Bona- 

 parte. Paris, 1800, (Annee 8), p. 284. 



