6 Composition of the Atmosphere 



experiments were wonderfully comprehensive and included a determina- 

 tion of the decrease in volume of a confined mass of air not only when 

 mixed with nitric oxide but when subjected to the action of alkaline sul- 

 phides, moist iron filings with and without an admixture of sulphur, phos- 

 phorus ignited and at room temperature, and precipitated ferrous hy- 

 droxide. His experiments with alkaline sulphides were somewhat more 

 extensive than with the other agents. In the first experiment he dissolved 

 alkaline liver of sulphur in water, poured 4 ounces of the solution into a 

 24-ounce bottle, which he corked well, then reversed the bottle, and im- 

 mersed its neck in a small vessel of water, keeping it in this position for a 

 fortnight. At the end of this time, without removing the bottle from the 

 water, he took out the cork, and the water at once rushed into the bottle. 

 By noting the amount of water thus added he was able to demonstrate 

 that in a fortnight, out of the 20 volumes of air in the bottle, 6 volumes 

 were lost. In a second experiment he reports that 4 parts were lost out 

 of 20, and at another time, when the bottle was corked for 4 months, there 

 were 6 parts lost out of 20. As the result of the third experiment agreed 

 with the first, the average of the three experiments shows a loss of approxi- 

 mately 6 parts out of 20, or 30 per cent. Scheele also exposed phosphorus 

 to a confined volume of air, allowing it to remain for 6 weeks, and found 

 that one-third of the air was lost. 



Of particular significance in the light of the main purpose of this mem- 

 oir is the fact the Scheele was the first to attempt a systematic study of the 

 composition of the atmosphere over a lengthy period. In 1779 he com- 

 municated to the Academy 1 in Stockholm the results of his investigation 

 of the preceding year. This communication was deemed of great impor- 

 tance by Lavoisier. 2 



The method employed by Scheele was to expose a confined volume of 

 air to the action of a mixture of 2 parts of iron filings and 1 part of pow- 

 dered sulphur, to which had been added a small amount of water. This 

 mixture produced in a few hours a diminution of the air greater than that 

 obtained by the sulphuret of potassium in several days. 3 Scheele used 

 this method to determine the degree of salubrity of the atmosphere at 

 different times of the year and to find out the proportion of "vital" air. 



From January 1 to March 23, 1778, atmospheric air was found to con- 

 tain 27.3 per cent of oxygen; on March 23, 24.2 per cent; on April 19, 20, 

 and 21, 30.0 per cent. During the months of May and June the quantity 

 of vital air was between 24 and 27 per cent; on October 5, during a very 

 heavy storm, it was found to be 30 per cent. From October 5 to Novem- 

 ber 4 the quantity of vital air was 24 to 27 per cent; and on November 4 

 and 5, with the barometer very high, it was 24 per cent. From November 



1 Scheele, Kongl. Vetenskaps-Academiens Handlingar, 1779, 40, p. 50. 



'Lavoisier, Recueil des Memoires de Lavoisier, 3, p. 154; and Oeuvres de Lavoisier, 

 1862, 2, p. 715. 



8 A figure of Scheele's apparatus is also given in F. Hoefer's Histoire de la chinfie, 2d 

 ed., Paris, 1869, 2, p. 453. 



