736 REPORT—1896. 
body, which in muriatic acid was combined with hydrogen, and for which he 
proposed the name ‘chlorine,’ derived from the Greek yAwpos, signifying ‘ green,’ 
the colour by which the gas is distinguished. 
The numerous communications which Humphry Davy made to the Royal 
Society on this subject form one of the brightest and most interesting chapters in 
the history of chemistry. They have recently been reprinted by the Alembic 
Society, and I cannot too highly recommend their study to the young students of 
our science. 
I need not remind those who have followed the history of chemistry how hotly 
and persistently Davy’s views were combated by a number of the most eminent 
chemists of his time, led by Berzelius himself; how long the chlorine controversy 
divided the chemical world ; how triumphantly Davy emerged from it; how com- 
pletely his views were recognised; and how very instrumental they have been in 
advancing theoretical chemistry. 
The hope, however, which Davy expressed in that same historic paper, ‘that 
these new views would perhaps facilitate one of the greatest problems in economi- 
cal chemistry, the decomposition of the muriates of soda and potash,’ was not to 
be realised so soon. Although it had changed its name, chlorine was still for 
many years manufactured by heating a mixture of salt, manganese, and sulphuric 
acid in leaden stills, as before. 
This process leaves a residue consisting of sulphate of soda and sulphate of 
manganese, and for some time attempts were made to recover the sulphate of soda 
from these residues, and to use it for the manufacture of carbonate of soda by the 
Le Blanc process. On the other hand, the Le Blane process, which had been dis- 
covered and put into practice almost simultaneously with Berthollet’s chlorine 
process, decomposed salt by sulphuric acid, and sent the muriatic acid evolved 
into the atmosphere, causing a great nuisance to the neighbourhood. 
Naturally, therefore, when Mr. William Gossage had succeeded in devising 
plant for condensing this muriatic acid, the manufacturers of chlorine reverted to 
the original process of Scheele, and heated manganese with the muriatic acid thus 
obtained. Since then the manufacture of chlorine had become a by-product of 
the manufacture of soda by the Le Blanc process, and remained so till very 
recently. 
For a great many years the muriatic acid was allowed to act upon native ores 
of manganese in closed vessels of earthenware or stone, to which heat could be 
applied, either externally or internally. These native manganese ores, containing 
only a certain amount of peroxide, converted only a certain percentage of the 
muriatic acid employed into free chlorine, the rest combining with the manganese 
and iron contained in the ore, and forming a brown and very acid solution, which 
it was a great difficulty for the manufacturer to get rid of. Consequently, many 
attempts were made to regenerate peroxide of manganese from these waste liquors, 
so as to use it over again in the production of chlorine. 
These, however, for a long time remained unsuccessful, because the exact 
conditions for super-oxidising the protoxide of manganese by means of atmospheric 
air were not yet known. 
Meantime, viz., in 1845, Mr. Dunlop introduced into the works created by his 
grandfather, Mr. Charles Tennant, at St. Rollox, a new and very interesting 
method for producing chlorine, which was in a certain measure a return to the 
process used by the alchemists. 
Indeed, the first part of this process consisted in decomposing a mixture of 
salt and nitre with oil of vitriol—a reaction that had been made use of for so many 
centuries! The chlorine so obtained is, however, not pure, but a mixture of 
chlorine with oxides of nitrogen and hydrochloric acid, which Mr. Dunlop had to 
find means to eliminate. 
For separating the nitrous oxides, Mr. Dunlop adopted the method introduced 
twenty years before by the great Gay-Lussac in connection with vitriol-making, 
viz., absorption by sulphuric acid, and the nitro-sulphuric acid thus formed he also 
utilised in the same way’as that obtained from the towers which still bear Gay- 
Lussac’s illustrious name, viz., by using it in the vitriol procesg in lieu of nitric 
