PRACTICAL USE OF LIME. 161 



added, inucli colouring- matter will be extracted, conferring" a 

 deep brown tint to the solution. Water alone, when heated 

 to the boiling- jjoint, will extract a little of this colour, but to 

 a comparatively trifling- extent. From these facts, and by 

 observing- that the alkali employed loses causticity and some 

 of its acrid taste, chemists have concluded that humus con- 

 tains an acid principle, to which the modern term " humic 

 acid" has been applied ; and if we admit that a combining- 

 power between alkalies and other substances in an opposite 

 state of electricity is sufficient to establish the presence of an 

 acid, we will not dispute the correctness of the term. 



But if, in lieu of any of these pure alkalies, lime be 

 employed, whether in powder or as strong- lime-water, colour 

 will be destroyed, and the supernatant liquid will become 

 A'ery pale. Thus, for example : — Take an ounce of any of 

 the three substances named ; mix with it a quarter of its 

 weig-ht of powdered quick-lime, and pour on the mass a pint 

 of boiling- rain-water. After stirring- to effectually blend the 

 whole, let the mixture repose for a time. At first the float- 

 ing- liquor will be turbid, but it will finally become clear, 

 and nearly void of colour. 



This experiment may justly be considered inconclusive, 

 for the eftect of the lime mig-ht be deemed neg-ative. How- 

 ever, having- pre])ared any of, or all, the brown liquids, that 

 is to say, the soluble humate of pofa.^tm, of soda, and of 

 (wi?)W7iia, take a known measure of any one of these, more 

 or less, and add to it either a small quantity of lime in 

 powder, or so much strong lime-water as shall be required to 

 produce the effect, which will speedily become sufficiently 

 evident. In either case a precipitate will be produced, and 

 the liquid will be nearly deprived of colour. 



Here we perceive a positive or direct action of the lime, 

 for it becomes evident that its affinity for the humic extrac- 

 tive or acid is so strong- as to take it from its alkaline base^ 

 ■whether that base has been potash, soda, or ammonia. 



The same phenomena will occur if common heath soil, 

 bog-, or turbary peat-moss be the subject of experiment. 

 Mr. Rowlandson announced these results in the Jotirnal of 

 Afjr'tcnJture, and I can vouch, by the evidence of repeated 

 experiments, that his conclusions are faithfid, so far, at least, 

 as they can be attested by solutions of any of the humous 

 substances obtainable in farm or horticultural establishments. 

 Further confirmation may be obtained by testing- that dark- 

 coloured liquid from farm dung-hills, which, throug-hout tho 



