Chemical Society. 519 



of caustic potash is substituted in this process for the carbonate, the 

 absorption of chlorine proceeds without interruption ; but the liquid 

 when saturated bleaches strongly from hypochlorite formed. A 

 long-continued boiling is required to destroy this property com- 

 pletely, and as oxygen escapes, the chlorate obtained must be de- 

 ficient iu quantity in a corresponding proportion. The process 

 which the author recommends, and which is attended with none 

 of these inconveniences, consists in mixing carbonate of potash inti- 

 mately with an equivalent quantity of dry hydrate of lime, and ex- 

 posing the mixture to chlorine gas. This mixture, although quite 

 drj^, absorbs the gas with prodigious energy, the temperature rises 

 much above 212°, and water is freely evolved. When saturated it 

 may be moderately heated, which destroys a mere trace of hypo- 

 chlorite it contains. The whole lime is found in the state of car- 

 bonate, and the potash as chlorate and chloride of potassium. The 

 solution of the two latter salts is neutral, without any bleaching 

 property, and free from lime. The chlorate of potash may be 

 crystallized from it in the usual way. Carbonate of potash, when 

 moistened and exposed to chlorine, without the hydrate of lime, ab- 

 sorbs the gas with great avidity, and certainly answers better than 

 a strong solution of the same salt ; but the absorption becomes 

 slow after the salt is in the state of bicarbonate, and subsequently a 

 large quantity of the bleaching hypochlorite of potash is produced. 

 In the new process described above, there is no reason to believe 

 that the carbonate of potash is decomposed by the dry hydrate of 

 lime till the chlorine is presented to the mixture ; then, while the 

 lime attracts the carbonic acid, the chlorine acts simultaneously 

 upon the potash, and the carbonate of potash is thus readily decom- 

 posed. The same principle of calling in a secondary agency to 

 promote combination may be taken advantage of in many other 

 cases. One of these, of some interest, is the promotion of the ab- 

 sorption of sulphuretted hydrogen by hydrate of lime, through the 

 influence of other salts. Thus hydrate of lime, dry or slightly 

 damped, ceases to absorb sulphuretted hydrogen long before it is 

 saturated with that gas ; but if mixed with an equivalent of hydrated 

 sulphate of soda, the absorption takes place with greatly increased 

 avidity, and goes on till two equivalents of sulphuretted hydrogen 

 are taken up for one equivalent of lime. But here, with the assist- 

 ance of sulphuretted hydrogen, the hydrate of lime decomposes the 

 sulphate of soda, sulphate of lime being formed, while caustic soda 

 combines with tlie sulphuretted hydrogen. 



The author has found that the last mixture may be applied with 

 advantage, from its great absorbing power, in purifying coal gas, 

 where the highest degree of purification is desirable, and where the 

 products, sulphate of lime and hydrosulphuret of sulphuret of sodium, 

 can be ceconomically applied. He recommends it to be introduced 

 into the last of the dry lime-purifiers. 



5. An extract from a letter from Olli ve Sims, Esq., Shelton, Stafford- 

 shire Potteries, was read, announcing a considerable and very accessi- 

 ble source of the hitherto very rare mineral, phosphate of yttria. 



