LEEDS chemists’ ASSOCIATION. 
449 
chloric acid, the fumes of which were for many years the bugbear of the alkali trade, 
affording an opportunity to landowners, needy or otherwise, to claim enormous damages 
for the injury done to trees, etc. on their estates by the hydrochloric acid gas. How¬ 
ever, the arrangements now made compulsory by Act of Parliament for passing the 
evolved gas into towers filled with coke, and having a stream of water flowing 
through them, have effectually remedied the difficulty, and supplied quantities of hydro¬ 
chloric acid somewhat larger than the demands of commerce, since several makers do 
not find it worth while to collect it, but charge their towers with limestone, which is 
converted into chloride of calcium, and runs off in a state of solution. 
The history of the soda manufacture is both interesting and instructive. There are at 
least four sources from which, in one country or another of the world, soda is produced. 
l.st. Native carbonate of sodium, found in Egypt, and known as “natron.” This is 
reasonably supposed to be the substance termed nitre in our translation of the Bible.* 
A somewhat similar salt is obtained in Hungary by lixiviating the soil. A native car¬ 
bonate of sodium is found in a remote part of India. I published an analysis of this 
(Pharm. Journ. vol. xii. p. 517), the chief interest of which consisted in its proving the 
salt to be a sesqnicarhonate. 
2nd. By the calcination of plants belonging to the Order Chenopodiacece, growing 
upon the seashore chiefly in Spain, the Canary Islands, etc. The product of this opera¬ 
tion, under the name barilla, used to be the chief source of soda for the supply of 
England. 
3rd. By burning in kilns certain seaweeds, on the coast of Scotland, Normandy, etc. 
Twenty-two tons of wet seaweed yield about a ton of ash, which is known as kelp. 
4th. Soda is made chiefly by the process of Leblanc, a discovery which dates ninety 
years back, and which, unlike almost every other manufacturing processs, is now what 
it was when first enunciated, the best and simplest method of effecting the object in view. 
The French revolution of 1793 compelled the attention of that nation to Leblanc’s 
process as a means of supplying to such vital industries as the soap and glass manufac¬ 
turers a substitute for the barilla previously used, but the importation of w^hich was 
•arrested. The influence of war, or other political unsettlement, upon the ordinary cur¬ 
rents of commerce is illustrated upon the large scale in the instance of the artificial pro¬ 
duction of soda by Leblanc’s method. 
Another and a curious example has occurred more recently, and is not generally 
known. Pimento grows spontaneously in Jamaica, and the only limit to its production 
is the existence of prices that will remunerate the labour of picking and preparing the 
fruit for market. Previous to the Crimean War, Kussia was our largest customer for 
pimento, it being used to flavour the bread generally eaten. The war interrupted this 
use, which has never been resumed, some substitute for pimento having been found. 
The outline of Leblanc’s process consists, as is well known, in forming sulphate of 
sodium by heating common salt with sulphuric acid, and calcining the sulphate of 
sodium thus formed with chalk and coal in a furnace. The chemical composition of the 
ilack-ash, as this product is termed, is enveloped in much doubt, the existence of an 
oxy-sulphide of calcium being urged by some authorities, and denied by later ones. 
However, when treated with warm water, the solution evaporated, and the dry salt cal¬ 
cined, a white soda-ash, consisting chiefly of carbonate of sodium, is obtained, which is 
the object of this most important branch of chemical industry An easy stage leads us 
now to the bicarbonate of sodium, indicated as our subject. The solution of alkali 
readily yields the soda crystals of commerce, and these being exposed to an atmosphere 
of carbonic acid, give up a part of their combined water, and absorb another equivalent 
of carbonic acid. 
Before alluding to other methods proposed for the manufacture of soda, I may call 
your attention to solid caustic soda as a substance which made its appearance in the 
market during the period between the International Exhibitions of 1851 and 1862. 
Mr. Dale conceived the ingenious idea of evaporating the weak solutions of caustic 
alkali by substituting them for the water used in feeding his steam-boilers, the solution 
being run off when it acquired a specific gravity of 1'25, and the evaporation to a specific 
gravity of 1'9 being conducted in open pans, when the liquor gives a solid product upon 
^ “ As vinegar upon nitre, so is he that singeth songs with a heavy heart.” (Prov. xxy. 20.) 
‘For though thou wash thee with nitre, and take thee much soap, yet,” etc. (Jerem. ii. 22.) 
