THE ALUMNI JOURNAL, 



281 



name of bleaching powder, which allowed 

 the bleaching powers of chlorine to be 

 transported to any distance. 



THE ART OF BLEACHING IN 1 799. 



In order to give you a conception of the 

 theoretical ideas prevalent at this time. I 

 will read to you a passage from an in- 

 teresting treatise on the art of bleaching 

 published in 1799, by Higgins. In his 

 chapter "On bleaching with the oxygen- 

 ated muriatic acid and on the methods of 

 preparing it," he explains the theory of 

 the process as follows; — 



"Manganese is an oxyd, a metal satu- 

 rated with oxygen gas. Common salt is 

 composed of muriatic acid and an alkaline 

 salt called soda, the same which barilla 

 afifords. Manganese has greater affinity 

 to sulphuric acid than to its oxygen and 

 the soda of the salt greater affinity to 

 sulphuric acid than to the muriatic acid 

 gas, hence it necessarily follows that these 

 two gases (or, rather, their gravitating 

 matter) must be liberated from their 

 former union in immediate contact with 

 each other ; and although they have but 

 a weak affinity to one another, they unite 

 in their nascent state, that is to say 

 before they individually unite to caloric, 

 and separately assume the gaseous state ; 

 for oxygen gas and muriatic acid gas 

 already formed will not unite when mixed 

 inconsequence principally of the distance 

 at which their respective atmospheres 

 of caloric keep their gravitating particles 

 asunder. The compound resulting from 

 these two gases still retains the property 

 of assuming the gaseous state, and is the 

 oxygenated muriatic gas." 



Interesting as these views may appear, 

 considering the time they were published, 

 you will notice that the role played by 

 the manganese in the process, and the 

 chemical nature of this substance, were 

 not at all understood. The law of multi- 

 ple-proportions had not yet been pro- 



pounded by John Dalton, and the re- 

 searches of Berzelius on the oxides of 

 manganese were only published thirteen 

 years later, in 1812. The green gas we 

 are considering was still looked upon as 

 muriatic acid, to which oxygen had been 

 added in contradistinction to Scheele's 

 view, who considered it as muriatic acid 

 from .'•omething, viz., phlogiston, had 

 been abstracted. 



davy's work on chlorine. 

 It was Humphry Davy who had, by a 

 series of brilliant investigations, carried 

 out in the laboratory of the Royal Institu- 

 tion between 1808 and 18 10, accumulated 

 fact upon fact to prove that the gas 

 hitherto called oxygenated muriatic acid 

 did not contain oxygen. He announced 

 in an historic paper, which he read be- 

 fore the Royal Society on July 12, 18 10, 

 his conclusion that this gas was an 

 elementar}' body, which in muriatic acid 

 was combined with hydrogen, and for 

 which he proposed the name "chlorine," 

 derived from the Greek, signifying 

 "green" the color by which the gas is 

 distinguished. 



The numerous communications which 

 Humphry Davy made to the Royal 

 Society on this subject form one of the 

 brighest and most interesting chapters in 

 the history of chemistry. They have re- 

 cently been reprinted by the Alembic 

 Society, and I cannot too highly re- 

 commend their study to the young stu- 

 dent ot our science. 



Those who have followed the history 

 of chemistry I need not remind how hotly 

 and persistently Davy's views were com- 

 bated by a number of the most eminent 

 chemists of his time, led by Berzelius 

 himself, how long the chlorine contro- 

 versy divided the chemical world, how 

 triumphantly Davy emerged from it, how 

 completely his views were recognized, 

 and how very instrumental they have 

 been in advancing theoretical chemistry. 



