656 
deposit. It is clear that to obtain thioureum from the compound V 
it is not even necessary to dissolve the latter first entirely. It already 
suffices to bring the compound in contact with water, because the 
pure saturated solution of V is metastable, and will deposit thioreum 
specially on seeding with a erystal of this substance, which con- 
version continues till the compound has quite vanished. 
With regard: to the exact relation between the pseudo-binary and 
the unary T, x-figure of the system NH, NCS—CS(NH,), we may 
state that it is being investigated, and that we hope that we shall 
soon be able to give it with perfect certainty. *) 
Anorg. Chem. Laboratory of the University. 
Amsterdam, Oct. 25, 1912. 
Botary. — “On the demonstration of carotinoids in plants. Second 
communication: Behaviour of carotinoids with regard to 
reagents and solvents.” By Prof. C. van WisskLincu. (Commu- 
nicated by Prof. J. W. Morr). 
(Communicated in the meeting of October 25, 1912). 
The reagents by means of which coloration is brought about in 
carotinoids are the following: concentrated sulphuric, sulphurous and 
concentrated nitric acids, bromine water, concentrated hydrochloric 
acid with a little phenol or thymol, and iodine in potassium iodide 
or chloralhydrate solution. All these reagents cause blue coloration, 
except the iodine reagents which generally produce a green colour. 
In this paper the use of sulphuric acid, bromine water and iodine 
in potassium iodide solution will be dealt with as well as two new 
reagents for carotinoids, namely, concentrated solutions of antimony 
trichloride and of zine chloride both in 25 °/, hydrochloric acid. 
Solvents as well as reagents can also be successfully used in the 
microscopic investigation of carotinoids, and they also are dealt with 
in this paper. 
Sulphuric acid. 
T. Tammes”*) in her investigation of carotin used concentrated 
1) This relation is probably pretty complicated, because different crystallized 
modifications exist of both pseudo-components. This was already known of NH, 
CNS, but for CS (NH,), it was revealed for the first time by this investigation. 
2) T. T'ammes, Ueber die Verbreitung des Carotins im Pflanzenreiche, Flora 
1900, 87. Bd. 2. Heft, p. 213. 
