358 REPORT—1899. 
Total absorption beyond 1 milligram-molecule in 100 c.c., 3 mm. thick, 
transmits rays very feebly from '/A 2000 to 2170, an absorption band 
occurs as far as 2780, the rays are transmitted from 1/A 2780 to 3070. 
Total absorption beyond. 
The absorption band continues until 4 mm. of 1 milligram-molecule in 
560 e.c., though much enfeebled. Beyond 3170 there is total absorption 
to about !/A 3630, with, as it were, another absorption band. It con- 
tinues to 2 mm. of milligram-molecule in 500 c.c. between 3200 and 3630, 
after which there is total absorption beyond '/A 3870. There is a very 
strong absorption beyond 3900. 
Tsatin crystals are deep red, like fused potassium dichromate. 
boss 
Methylpseudoisatin, CoH oo. 
N(CH.) 
There is complete absorption of all rays by 10 mm. of 1| milligram- 
molecule in 100 cc. By 5 mm. the strong rays between !/A 2740 and 
2900 are transmitted, all rays beyond are totally absorbed. There is a 
strengthening of the transmitted rays by thicknesses of 4 mm. and 3 mm. 
between !/X 2740 and 2970. Total absorption beyond. 
At 2 mm. and 1 mm. the absorption of rays less refrangible than !/X 
2740 is much diminished, that is to say, the absorption band hereabouts is 
weakened. 
By thicknesses of 5, 4, 3 mm. of 1 milligram-molecule in 500 c.c. 
there is nothing transmitted beyond !/A 3030, except the very strong line 
at 3600. There is very strong absorption beyond this line until we get 
to 4 mm. of 1 milligram-molecule in 2,500 c.c., when the rays between !/\ 
3600 and 3840 are feebly transmitted, and there is only a very feeble 
transmission of strong rays beyond lying between 1/A 4250 and 4400, and 
so gradually the absorption diminishes. 
Methylpseudoisatin has a colour more resembling cinnabar than 
potassium dichromate. 
CO 
Methylisatin, CHC Sco + CH,. 
iA 
With 1 milligram-molecule in 100 c.c, there is a total absorption of 
rays down to a thickness of 10 mm. : 
At 5 mm, there is a very feeble transmission of rays between 1/X 
2000 and 2170. 
At 3 mm. it is evident that avery strong absorption band lies between 
2180 and about 3350, when rays are very feebly transmitted, all beyond 
3470 being totally absorbed. 
This absorption band gradually diminishes in intensity, but more rapidly 
on the part of the rays of shorter wave-length than is the case with those 
lying between !/X 2270 and 2870. For instance, 2 mm. of liquid con- 
taining 1 milligram-molecule in 500 c.c., absorbs the rays between 1/d 
2600 and 2770. Total absorption is seen beyond 3600. 
Methylisatin is orange red, like powdered potassium dichromate. 
