a 
TRANSACTLONS OF SECTION B. 739 
chemistry—the science of to-day—endeavoured to determine the place of Scheele’s 
gas in the new theory. Lavoisier was of opinion that all acids, including muriatic 
acid, contain oxygen. SBerthollet found that a solution of Scheele’s gas in 
water, when exposed to the sunlight, gives off oxygen and leaves behind muriatic 
acid, He considered this as proof that this gas consists of muriatic acid and 
oxygen, and called it oxygenated muriatic acid. 
In the year 1785 Berthollet conceived the idea of utilising the colour- 
destroying powers of this gas for bleaching purposes. He prepared the gas by 
heating a mixture of salt, manganese, and vitriol. He used a solution of the gas 
in water for bleaching, and subsequently discovered that the product obtained by 
absorbing the gas in a solution of caustic potash possessed great advantages in 
practice. 
This solution was prepared as early as 1789, at the chemical works on the 
Quai de Javelle, in Paris, and is still made and used there under the name of 
é Kau de Javelle,’ 
James Watt, whose great mind was not entirely taken up with that greatest 
of all inventions—his steam-engine—by which he has benefited the human race 
more than any other man, but who also did excellent work in chemistry—became 
acquainted in Paris with Berthollet’s process, and brought it to Scotland. Here 
it was taken up with that energy characteristic of the Scotch, and a great stride 
forward was made when, in 1798, Charles Tennant, the founder of the great firm, 
which has only recently lapsed into the United Alkali Company, began to use 
milk of lime, in place of the more costly caustic potash, in making a bleaching 
liquid; and a still greater advance was made when, in the following year, 
Tennant proposed to absorb the chlorine by hydrate of lime, and thus to produce 
a dry substance, since known under the name of bleaching powder, which allowed 
the bleaching powers of chlorine to be transported to any distance. 
In order to give you a conception of the theoretical ideas prevalent at this 
time, I will read to you a passage from an interesting treatise on the art of 
bleaching published in 1799 by Higgins. In his chapter ‘On bleaching with the 
oxygenated muriatic acid, and on the methods of preparing it’ he explains the 
theory of the process as follows :— 
‘ Manganese is an oxyd,a metal saturated with oxygen gas. Common salt is 
composed of muriatic acid and an alkaline salt called soda, the same which barilla 
affords. 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, in consequence 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 pub- 
lished, you will notice that the réle played by the manganese in the process and 
the chemical nature of this substance were not at all understood. ‘The Jaw of 
multiple proportions had not yet been propounded by John Dalton, and the 
 vesearches 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 which something, viz., phlogiston, 
had been abstracted. 
It was Humphry Davy who had, by a series of brilliant investigations carried 
out in the Laboratory ot the Royal Institution between 1808 and 1810, accumu- 
lated 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 before 
the Royal Society on July 12, 1810, his conclusion that this gas was an elementary 
