458 CHEMISTRY. [Nov. 



HOW TO MAKE POTASH. 



BAEON FEED. VON MUELLEE, K.C.M.G., of Victoria, writes 

 as follows liow to make potash. The wood, bark, branches, 

 and foliage are burnt in pits sunk 3 feet or 4 feet in the ground ; 

 the incineration is continued until the pit is almost filled with 

 ashes. Young branches and leaves are usually much richer in 

 potash than the stem-wood, hence they should not be rejected. 

 The ashes thus obtained are placed in tubs or casks on straw 

 over a false bottom. Cold water, in moderate quantities, is poured 

 over the ashes, and tlie first strong potash liquid removed for 

 evaporation in flat iron vessels, while the weaker fluid is used 

 for the lixiviation of fresh ashes. While the evaporation proceeds, 

 fresh portions of strong liquid are added until the concentrated 

 boiling fluid assumes a rather thick consistence. At last, with mild 

 heat and final constant stirring, the whole is evaporated to dryness. 

 This dried mass represents crude potash, more or less impure, 

 according to the nature of the wood employed. A final heating 

 in rough furnaces is needed to expel sulphur combinations, water, 

 and empyreumatic substances ; also, to decompose colouring prin- 

 ciples. Thus pearlash is obtained. Pure carbonate of potassa in 

 crude potash varies from 40 to 80 per cent. Experiments, so far 

 as they were instituted in the laboratory, have given the follow- 

 ing approximate result with respect to the contents of potash in 

 some of our most common trees : — The woods of the casuarinas, or 

 she-oaks, as well as that of the black or silver wattle, are somewhat 

 richer than the wood of the British oak, but far richer than the 

 ordinary pine woods. The stems of the Victorian blue gum and 

 the so-called swamp tea-tree {Melaleuca ericifolia) yield about as 

 much potash as European beech. The foliage of the blue gum 

 proved particularly rich in this alkali, and as it is heavy and easily 

 collected at the sawmills, it might be turned there to auxiliary 

 profitable account, and, indeed, in many other spots of the ranges. 

 In the Queensland coast country the mangrove could be made to 

 yield potash in immense quantities, as it is richer in this alkali 

 than almost any other native tree or shrub ; and even if the man- 

 grove were not used for the manufacture of potash, the ash being 

 rich in this valuable fertilizer, could be easily and economically 

 applied for manurial purposes. Of course, British woodmen are 

 aware that it is hopeless to compete with the extensive mineral 

 deposits in Germany whence most of the potash of commerce is now 

 made. 



