468 BACTERIOLOGICAL CHEMISTRY 



the case of mould fermentations) may give rise to a range 

 of colours : — 



(a) Yellow colours (canary to orange yellow) usually 

 indicate the presence of hydroxy-acids, such as gluconic, 

 citric, malic or lactic acids. 



(b) Blue or violet colours usually indicate phenolic 

 acids . 



(c) An intense blood-red colour is given by kojic acid 

 (see p. 294). 



{d) An intense green or black-green is given by citro- 

 mycetin. 



(e) A rusty brown-coloured precipitate soluble in 

 excess of ferric chloride to give an iodine brown-coloured 

 solution is given by citrinin (see p. 159). 



The presence of unsaturated products may be detected 

 by the addition of bromine water, which is decolorised in 

 their presence. 



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