ONE HUNDRED YEAES OF CHEMISTRY 297 



many oxidations and reductions. We owe to Mohr some 

 improvements in apparatus and a German text-book on 

 the subject, while Sutton wrote an excellent English work 

 on volumetric analysis, of which many editions have 

 appeared. 



While volumetric analysis began to be used less than 

 one hundred years ago, its applications have been grad- 

 ually extended to a very great degree, and it is not only 

 exceedingly important in investigations in pure chemis- 

 try, but its use is especially extensive in technical labora- 

 tories where large numbers of rapid analyses are 

 required. 



Not a few volumetric methods have been devised or 

 improved in the United States, but mention will be made 

 here only of'Cooke's important method for the deter- 

 mination of ferrous iron in insoluble silicates, published 

 in the Journal (44, 347, 1867) ; to Penfield's method for 

 the determination of fluorine in 1878; and to the more 

 recent general method of titration with an iodate in 

 strong hydrochloric acid solutions, due to L. W. 

 Andrews, a number of applications of which have been 

 worked out in the Sheffield Laboratory. 



A considerable amount of work with gases had been 

 done by Priestley, Scheele, Cavendish, Lavoisier, Dalton, 

 Gay-Lussac, and others before our hundred-year period 

 began. Cavendish, about 1780, had analyzed atmos- 

 pheric air with remarkable accuracy, and had even sep- 

 arated the argon from it and wondered what it was, and 

 later Gay-Lussac had shown great skill in the study of 

 gas reactions. During our period gas analysis has been 

 further developed by many chemists. Bunsen, in par- 

 ticular, brought the art to a high degree of perfection in 

 the course of a long period beginning about 1838, the last 

 edition of his "Methods of Gas Analysis" having been 

 published in 1877. 



Important devices for the simplification of gas-analy- 

 sis in order that it might be used more conveniently for 

 technical purposes have been introduced by Orsat in 

 France and by Winkler, Hempel and Bunte in Germany. 



It appears that our countryman Morley has surpassed 

 all others in accurate work with gases in connection 

 with his determinations of the combining weights and 



