LITMUS. 169 



drachm. Fluid extract : Dose, 1-4 drachms. Com- 

 pound powder B.P. : Dose, 1-2 drachms. Solid extract 

 in form of sticks is known as Liquorice Juice. 



Distinctive character The root varies in size and 

 character. The English-grown root is usually sold 

 fresh. It is greyish brown externally, with transverse 

 scars, and internally yellowish and fibrous. The trans- 

 verse section shows a radiate structure. The taste is 

 sweetish, and the odour, when chewed, pea-like, but 

 characteristic. The root of commerce often contains, 

 especially the Spanish and Russian sorts, a large pro- 

 portion of underground stem, which is less sweet and 

 can be recognised by the absence of transverse scars, 

 and the presence of a central pith. The Russian and 

 Persian Liquorice are often in large pieces, f-i inch or 

 more in diameter, and has a red-brown scaly surface, 

 and a slight bitterness and acridity. They are derived 

 from G. glabra, var., glandulifera, W. and K. The Russian 

 sort is also sold in a decorticated state. 



LITMUS. Roccella tlnctoria and R. Montagnel, D.C. 



T-, . N.O. Lichtnes. 



Syn. Lacmus, Persio. 



Part used Pigment. 



Used as an analytical indicator. The prepared Litmus 

 is made into various forms, such as papers or tinctures, 

 and as such used in chemistry for testing purposes. 

 The blue colour, which is natural, has the property of 

 turning to red whenever substances of an acid character 

 are brought into contact with it. This acquired red 

 colour will again return to blue in contact with alkalies. 

 This colouring matter is of a pure deep blue colour, and 

 is usually sold in the form of small cubes, or in a pre- 

 pared solution. It is prepared from Roccella tinctoria, D.C., 

 and R. Montagnei, D.C. 



Cudbear is a purplish red powder prepared from 

 Lecanora tartarta, Ach., and L.parella, Ach., and Archil 

 or Orchil is an ammoniacal, reddish purple liquid pre- 

 paration made from the same lichens. 



