402 MARION I. NEWBIGJN. 



a permanent loss of the power of giving a blue colour with 

 acid. To these points we shall return after considering the 

 characters of the green acid solution. 



(c) The Green Acid Solution. — The deep green solution 

 produced by adding excess of acid yields no pigment to ether. 

 On adding ammonia, and again shaking with ether, unaltered 

 chgetopterin of brownish-green tint is extracted by the ether. 

 On the addition of marble to the acid solution a precipitate 

 falls of dull green colour. This dissolves in methylated spirit 

 to form a green solution with a mere trace of fluorescence. 

 The spectrum shows four bands : the band in the red is exceed- 

 ingly strong; the other three have the same position as in un- 

 altered chsetopterin, and vary greatly in intensity. The position 

 of the band in the red is as follows : 



A 666 - X 634, c. = A 650. 

 The band has thus much the same position as the first band in 

 fig. 2 would have if the shadow to tlie right were to become 

 distinct. The addition of acid to this solution does not change 

 the position of the band in the red, but it ultimately turns the 

 solution a brownish colour. 



When the dull green precipitate obtained by the addition of 

 marble is treated with methylated spirit, there remains un- 

 dissolved a brownish residue which is insoluble in ether or 

 methylated spirit, and which is unaffected by acid or alkali. 

 A trace of similar residue remains when the precipitate from 

 the blue acid solution is treated with methylated spirit or 

 ether. 



General Conclusions as to the Action of Acids. 



If we snrvcy generally the action of acid on solutions of 

 chsetopterin, we see that the pigments precipitated respectively 

 from the blue and green acid solutions by the action of marble, 

 agree with one another, and diff'er from the original chaetopterin 

 in forming in methylated spirit solutions which are pure green 

 or bluish green in colour, very slightly fluorescent, and which 

 turn brown and not blue or green on the addition of acid. 

 They differ from chajtopterin and from each other in the 



