520 
PROFESSOR A. H. CHURCH OH TURACIN 
Fig. 4. Spectrum of a weaker solution prepared as above. 1st band, or a : shading 
begins at 577, is dark at 573, extends dark to 553'5, is shaded off to 549 ; centre of 
band n = 562. 2nd band, or f3 : begins to be shaded at 538, is dark at 533, extends 
dark to 514, is shaded of to 506 ; centre of band (3 = 523. 
Fig. 5. Spectrum of a strong solution of pure isolated turacin in faintly ammoniacal 
water. Note the occurrence, beside the band 8 already described, of a fourth and 
stronger, though narrower, band y near the line D. Measurements :—Band y : 605 
to 589 : centre 597. Band a: shading begins at 581, is black 577, extends black to 
547 ; there is a shaded space from 547 to 540. Band /3 ; extends from 540 to 506, is 
shaded to 503. Band 8 extends from 494 to 473. 
Fig. 6. Spectrum of a weaker solution of turacin than that shown in fig. 5, but pre¬ 
pared in the same way. Measurements :—Band y : 605 to 589. Band a : begins to 
be shaded at 577, is black at 573, extends black to 552, is shaded off to 547 ; centre 
at 562. Band (3 : begins to be shaded at 540, is dark at 533\5, extends dark to 511, 
is shaded off to 506 ; centre at 523. Band 8 extends from 494 to 473. 
Fig. 7. Spectrum of a solution, prepared in the year 1868, of turacin in weak 
ammonia water. Measurements : Band y, 605 to 589. Band «.: begins to be shaded 
at 579, is black at 573, extends black to 552, is shaded off to 549 ; centre at 562. 
Band /3 : begins to be shaded at 540, is dark at 535, extends dark to 514, is shaded 
off to 506 ; centre at 523. Band 8 extends from 494 to 473. 
[The bands y and 8 in the spectra are shown too dark in the figures — 8 is, in fact, 
barely perceptible.] 
The general results of these spectrum observations may be summarised thus :— 
Turacin, as it exists in the feathers, possesses two absorption bands, one of which ; 
a, is rather darker and less wide than the other, and is situated about the line D, 
extending some distance on its more refrangible side; the other band, /8, lies between 
the first-named and the line b. Turacin in alkaline solution always shows the same 
two bands, the first being, as before, darker and narrower than the second, but both 
bands are shifted towards the more refrangible end of the spectrum. When an 
alkaline solution of turacin is weak, it shows the above-named pair of bands only ; 
when its strength is increased, a third band, 8, faint but broad, appears near the 
line F. But if some isolated and dried turacin be dissolved in weak ammonia water, 
a liquid is obtained which, if strong enough to show the band 8, will also show a 
fourth band, y, darker and much narrower than 8, and situated on the less refrangible 
side of D. The recognition of the bands 8 and y is due to Dr. MacMunn ; the 
remaining features of these spectra were figured in my previous memoir, but with 
less completeness and exactitude. A question arises as to whether the band y—which 
is not seen in the spectra of turacin solutions freshly and directly prepared from the 
feathers, but only in the spectra of solutions of such turacin as had been previously 
isolated and dried—belongs to the unaltered pigment, or whether its occurrence is a 
sign of the presence of a decomposition or oxidation-product of turacin. The spectral 
