68 • REPORT— 1870. 



action, and a redistribution of the constituents takes place, until the whole of the 

 insoluble salt that can be formed is formed and precipitates. If one of the new- 

 compounds is so sparingly soluble that it crystallizes out, it is inferred that a fur- 

 ther redistribution must also take place tUl the amount that the water holds in 

 solution is sufficient to balance what remains of the original compounds. This is 

 what has been termed " reciprocal decomposition." 



In most cases that have been examined, this action takes place rapidly, the 

 balance being attained apparently as soon as the salts ai'e thoroughly mixed ; in 

 other cases, however, the action will go on for minutes, hours, or even days. 

 Quantitative experiments had been made on the rate of formation of ferric meco- 

 nate, ferric ferrocyanide in oxalic acid, potassio-iodide of platinum, the sulphates 

 of barium, strontium, and calcium, oxalate of magnesium, and acid tartrate of 

 potassium. It was found that where aU four compoimds remain in solution, the 

 amount of new salt produced in equal periods of time becomes gradually less and 

 less till the limit is very slowly attained ; but where one of the new compounds 

 crj'stallizes out, the maximum of chemical change is not at the commencement of 

 the action but after a certain quantity of crj'stals have been already deposited. In 

 this latter case many circumstances of a mechanical nature affect the rate, which 

 do not influence the decomposition when all the conipomids continue in solution ; 

 but a rise of temperature was found in both cases greatly to accelerate the chemical 

 action. 



On the Soda Manufacture. By "W. Gossage. 



This contribution was a supplement to a paper on the same subject read at Man- 

 chester in 1861, noticing various improvements connected with the processes of 

 ' manufacturing soda during the lapse of nine years since that period, and giving 

 also some details of the increase which has taken place in the extent of this impor- 

 tant manufacture during that time. One of the most important events has been 

 the passing of " The ."Ukali Act, 186.3," rendering it imperative that manufacturers 

 decomposing common salt for the production of sulphate of soda, should condense 

 not less than 95 per cent, of the hydrochloric acid gas evolved by such decompo- 

 sition. In the former paper, the means the author had devised and carried into 

 successful operation in the year 1836, for effecting such condensation, were de- 

 scribed, these means being now adopted imiversally, and so successfully that, in 

 many instances, this condensation exceeds 99 per cent. The most important use 

 for the hydrochloric acid obtained by sucli condensation is the manufacture of hypo- 

 chlorite of lime, or bleaching powder, the demand for wliich has taken an extra- 

 ordinary development since the introduction of straw. Esparto grass, and some 

 other substances than rags for the manufacture of paper. At the date of the pre- 

 vious paper, the chlorine was obtained by the action of hydrochloric acid on per- 

 oxide of manganese. Recently Mr. Walter Weldon, of Loudon, has perfected a 

 process by which peroxide of manganese is obtained from the chloride of man- 

 ganese prodnced by the action of hydrochloric acid on peroxide of manganese ; 

 and this process has been successfully carried into practice in this district, also in 

 that of Newcastle, and it has already been adopted by some of the largest manu- 

 facturers in both localities. Allusion was then made to Mr. Deacon's very scien- 

 tific process for the manufacture of chlorine without the use of manganese. Mr. 

 James Hargreaves, of Widnes, has also devised means for producing chlorine with- 

 out the use of oxide of manganese. The iron slag is treated with hydrochloric 

 acid, and thereby protochloride of iron in solution is obtained as a by-product, 

 which is evaporated, producing dry jirotochloride ; and this, hj slow application of 

 heat with access of atmospheric air, becomes perchloride, which undergoes decom- 

 position, yielding chlorine and peroxide of iron. In the former paper it was re- 

 marked that nearly all the sulphur used in this manufacture, the cost of which is 

 about equal to two fifths of the total cost of 'materials required, was reobtained in 

 combination with calcium, forming what is expressively designated as "alkali- 

 waste ;" and it was noticed, also, that this presented a problem worthy of attention 

 for its solution. Mr. L. Mond has made a near approximation to the solution of 

 this problem. His process consists in causing atmospheric air to be brought into 

 intimate contact with the alkali-waste as this is left in the lixiviating vats after 



