WRITINGS OF JAMES SMITHSON. 61 



The red cabbage, and the rind of the long radish are also 

 coloured by this principle. It is remarkable that these, on 

 being merely bruised, become blue ; and give a blue infu- 

 sion with water. It is probable that the reddening acid in 

 these cases is the carbonic ; and which, on the rupture of 

 the vessels which enclose it, escapes into the atmosphere. 



Of sugar-loaf paper. 



This paper has been employed by Bergman as a chemical 

 instrument. I am ignorant of what it is coloured with. 



Sulphuric, muriatic, nitric, phosphoric, and oxalic acids 

 make it red. Tartaric and citric acids, made rather yellow 

 spots than red ones. Distilled vinegar, and acid of amber, 

 had no aftect on it. 



Carbonate of soda and caustic potasb did not alter the 

 blue colour of this paper. 



Water boiled on this paper acquired a vinous red colour; 

 carbonate of lime put into this red liquor, did not affect its 

 colour : nor did carbonate of soda or caustic potash change 

 it to blue or green. 



Cold dilute sulphuric acid extracted a strong yellow tinc- 

 ture from this boiled paper : carbonate of lime put to this 

 yellow tincture made it blue ; but on filtering, the liquor 

 which passed was of a dirty greenish colour; and sulphuric 

 acid did not make it red : a blue matter was left on the 

 filter, which was not made red by. acetous acid ; but was so 

 by sulphuric. 



After this treatment the paper remained brown ; seem- 

 ingly such as it was before being dyed blue. 



It should seem that there are at least two colouring mat- 

 ters in this paper; one red, which is extricable from it by 

 water ; the other blue, which requires the agency of an acid 

 to extract it. 



Its insolubility in water, and low degree of sensibility to 

 acids, distinguish the blue matter from turnsol ; to which its 

 not being affected by alkalis otherwise much approximate 

 it. Its easy solubility in dilute suphuric acid, and being 



