Intelligence and Miscellaneous Articles. S-iS 



coloured from foreign rhubarb. It is totally soluble in alcohol and 

 sether, which by evaporation leave rhabarbaric or erythrosic acid, 

 forming with the alkalies red or purple compounds applicable to the 

 arts and to pharmacy. After drying, it has the appearance of ag- 

 glomerated powder of rhubarb ; when beaten in a mortar, the par- 

 ticles flatten and acquire a strong shining appearance. This substance 

 is perfectly tasteless, the odour slightly aromatic and nitrous, pro- 

 bably owing to the presence of a little nitric acid, which repeated 

 washings are incapable of separating. 



When heated in a glass tube, abundant yellow vapours of rha- 

 barbaric acid are produced, which soon condense into a yellowish 

 film in the tube, leaving a white residue of lime, which is stronger 

 in foreign erythrosin than in indigenous. 



Water has but little action on erythrosin ; it becomes merely 

 slightly yellow ; but if it be heated to ebullition, it acquires a reddish 

 amber tint, and becomes slightly acid. This acidity appears to be 

 owing to a small quantity of nitric acid, unremoved by repeated 

 washings; for it cannot be attributed to rhabarbaric acid, the quan- 

 tity of which is very small. When evaporated to a certain extent, 

 the liquor deposits gelatinous matter, which has all the characters of 

 pectin. 



When cold, alcohol acts but slightly on erythrosin, acquiring 

 merely ao amber tint ; but if it be boiled, the colour deepens and 

 acquires the reddish tint of Malaga wine. It requires seven or eight 

 times boiling to deprive erythrosin of all soluble matter. The first 

 and last washings redden litmus paper. 



As evaporation j)roceeds, alcohol deposits yellowish flocculi, pel- 

 licles of a crystalline appearance forming on the surface : but cry- 

 stals do not form on cooling ; a dry product can be obtained only 

 by evaporation to dryness. This so obtained has the form of gra- 

 nular pulverulent matter, of a brownish yellow colour, and somewhat 

 resembling Spanish snufF in appearance : its smell is slightly aro- 

 matic ; its taste rather acid and mucilaginous, but not at all lik^. that 

 of rhubarb. 



This matter, when repeatedly treated with aether and heated, 

 totally dissolves ; by evaporation a sulphur-coloured granular sub- 

 stance is obtained, which has a slightly aromatic odour, and the 

 surface of which, by exjjosure to the air, acquires an orange tint : it 

 possesses all the physical and the principal chemical characters attri- 

 buted to rhabarbaric acid by Brandes, and to rhabarbarin by Geiger. 



Indigenous and foreign rhubarb yielded perfectly similar products, 

 excepting that indigenous rhubarb gave most. Of two samples tried, 

 the foreign gave 60 per cent, and the indigenous 85 per cent, of 

 erythrosin ; but this did not occur in all cases. 



When a gramme of erythrosin is added to half a gramme of pot- 

 ash dissolved in fifteen grammes of water, the liquor soon becomes 

 of a reddish purple colour, which is more or less intense according 

 to the kind of rhubarb employed ; some days are required to com- 

 plete the operation. Its colouring power is so great, that one 

 gramme of erythrosin is sufficient to impart a more brilliant colour 



