CHEMICAL APPARATUS AND PRODUCTS. 201 



gress. Minerals were first systematically analyzed by Bergman at 

 Upsala, the results being published between 1777 and 1780, and 

 the processes were much improved and extended by Klaproth in 

 Berlin, and also by Berzelius. 1 he use of the blowpipe was pointed 

 out by Gahn, who undertook the experiments at the suggestion of 

 Bergman. The careful analysis of minerals led to the discovery 

 of many new elements, and the processes have been undergoing 

 improvement by a succession of chemists until the present hour. 



The application of electricity to the decomposition of chemical 

 substances resulted in the discovery by Davy of the metals of the 

 alkalies, potassium, sodium, and lithium, and of the alkaline earths 

 barium, strontium, calcium, and magnesium, and although he failed 

 in the decomposition of alumina, glucina, yttria, and zirconia, they 

 were suspected to be metallic oxides, which was afterwards proved 

 to be the case. Davy also showed that chlorine was not a com- 

 pound but an elementary body, and the subsequent discovery of 

 iodine and bromine, and the acids that they produce when com- 

 bined with hydrogen, proved that Lavoisier's notion that oxygen 

 was the sole acidifying principle was erroneous. The balance 

 belonging to the Royal Institution, and used by Young, by Davy, 

 and by Faraday, is in the Collection. 



As early as 1699 Homberg showed that equal quantities of an 

 alkali required different amounts of various acids to completely 

 neutralise them. These results attracted little or no attention at 

 the time, and even in 1777., when Wenzel published the results of 

 a careful set of experiments in which he determined the quantities 

 of two pairs of neutral salts that were adequate to decompose one 

 another with formation of two other neutral salts, the minds of 

 chemists were so much occupied with the discussion of the phlogistic 

 and anti-phlogistic theories, that no notice was taken of his work. 

 The fact that many chemists endeavoured to determine the exact 

 composition of salts is evidence of the belief of the constancy of 

 composition of chemical substances. In 1804 Dr. Dal ton pro- 

 posed to explain the uniformity of composition by assuming that 



