44 On the Rhus Glabrum and Sambucus Canadensis. 



to the consistence of a syrup, taking care not to burn it. Then 

 add to it an equal quantity of alcohol ; this will unite with the 

 acid, leaving the mucilage and other impurities behind. An 

 equal quantity of water is now to be added, and the whole dis- 

 tilled to obtain the alcohol. The malic acid will be left in 

 the retort, which may be poured out when cold. 



I have also examined the juice of the elder-berries, which 

 seems to possess important properties as a delicate reagent. 

 The following process was employed : 



Take any quantity of the ripe berries, picked clean from the 

 stalks, and after having bruised them, press the juice into a 

 clean well tinned vessel. Add a fourth part of its weight of 

 alcohol, and evaporate the mixture to about one-half. Re- 

 move it from the fire for ten or twelve minutes, and add as 

 much alcohol as you have of concentrated juice. A copious 

 precipitation of the parenchymatous and gummy parts will 

 take place, which will permit the liquor to be strained with 

 ease through a fine cotton cloth. 



The filtered liquor is now fit for use. It consists of the sac- 

 charine and colouring principles of the berries, in solution with 

 alcohol and water. It is of a beautiful violet colour. In or- 

 der to ascertain its utility as a test of acids and alkalies, the 

 following experiments were made : 



To one pint of rain-water a single drop of the tincture of 

 elder-berries was added. The blue colour was too pale to be 

 perceived ; but the addition of a single drop of sulphuric acid 

 produced a decided red colour. 



To the liquor employed in the last experiment, a minute 

 quantity of alkali was added, when it immediately changed to 

 a bright lively green. If a quantity barely sufficient to neutral- 

 ize the acid be employed, the original blue or violet colour is 

 restored ; hence this test possesses all the delicacy of the tinc- 

 ture of litmus, or blue cabbage, and has this additional va- 

 luable property of keeping unaltered, during the hottest season 

 of the year. 



