On the Alkalies of Commerce. 177 



it intd the small tin measure, which \ ou then fill np with 

 water ; pour it back again into the glass, in which you must 

 still pour a measure full of pure water : stir this new mix- 

 ture also three or four times within half an hour, in order 

 to facilitate the precipitation of a slight sediment, which 

 soon falls down. This sediment being completely formed, 

 slope the glass with caution, in order to fill with clear 

 liquor the small measure ; then empty this last into another 

 large glass ; after this place round the edges of a plate 

 drops of syrup of violets; pour also into the alkali-meter 

 test liquor until the line marks : take it afterwards with 

 the left hand, inclining it upon the glass which contains the 

 moiety of the clean alkaline solution : the acid liquor will fail 

 into it by hasty drops, or in a very small thread, which vou 

 may moderate at pleasure by retarding the entrance of the air 

 at the lateral hole or vent, upon which must be placed the end 

 of the finger; at the same time, with a small stick or match 

 assist the mixture, and facilitate the development of the car- 

 bonic acid, which is manifested by effervescence. When you 

 have emptied the alkali-meter to about the line marked 40, try 

 if the saturation approaches, by drawing your small stick 

 from the mixture and resting it upon one of the drops of 

 syrup of violets, which should become green if the potash 

 is not of a very inferior quality. If, on the contrary, the 

 violet colour is not altered, or, what would be worse, if it 

 be changed into red, there would be in the first case an indi- 

 cation of saturation, and in the second a proof of super- 

 saturation. Ijut this is not the case with good potashes : 

 at that line, the liquor tried can alter the syrup of violets 

 into green only ; or cause to return to the violet, and even to 

 the green, the drops which had been changed into red at 

 the time of a former trial : we must, therefore, in general 

 add more acid, which occasions a new effervescence; this 

 addition must be always made with caution, and we must 

 touch every time a droj) of syrup of violets in order to stop. 

 When at last the latter assumes a red hue, then, after havino" 

 restored the alkali-meter to a perpendicular position, in order 

 to see at what line the testing liquor stops, you must reckon 

 Vol. 28. No. 110. July I8O7. M one 



