VI CONTENTS. 
Ghemistry. A. W. K. pr Jone: “Action of sunlight on the einnamie acids”. 1274. 
CINNAMIC AcIps (Action of sunlight on the). 1274. 
crncLEs (Systems of) determined by a pencil of conics. 1107, 
COHEN (ERNST). The metastability of the metals in consequence of allotropy, and 
its significance for Chemistry, Physics and Technics, IT. 200. 
— presents a paper of Dr. H. R. Kruyr: “Current potentials of electrolyte 
solutions”. 615. 
— presents a paper of Dr. H. R. Krurr: “Electric charge and limit value of 
colloids”. 623. 
— presents a paper of Dr. H. R. Kruyt and Jac. van DER Spek: “The connection 
between the limit value and the concentration of arsenic trisulphide sols”. 1158. 
— The allotropy of bismuth. IL. 1236. 
— and J. C. van pen Boscu. The allotropy of antimony. I. 645. 
— and G. pe Bruin. The metastability of the metals in consequence of allotropy 
and its significance for Chemistry, Physics and Technics. III. 926. 
— and W. D. Hentperman. The allotropy of Cadmium. IL. 54. LIL. 122, IV. 638. 
V. 1050. 
— The allotropy of zinc. IL, 59. II. 541. 
— The allotropy of copper. IL. 60. 
— The allotropy of lead. I. 522. Note 1055. 
— The metastability of the metals in consequence of allotropy and its significance 
for Chemistry, Physics and Technics. IV. 1238. 
— and S. Worrr. The allotropy of potassium. L. 1115. 
COHEN (w. p.) and J, Bérsexen. The reduction of aromatic ketones. IIT. Contri- 
bution to the knowledge of the photochemical phenomena. 849. 
coLLorps (Electric charge and limit value of). 623. 
COLORATION (The) of some derivatives of Picrylmethylamide with alkalies. 647. 
coLours (On FresNEr’s coeflicient for light of different). Ist part. 415. 
COMPOUND (A crystallized) of isoprene with sulphar dioxide. 585. 
COMPOUNDS of arsenious oxide. I, 1111. 
CONCENTRATION (The connection between the limit value and the) of arsenic trisulphide 
sols. 1158. 
CONGRUENCE (A bilinear) of rational twisted quinties. 1250. 
CONGRUENCES (Some particular bilinear) of twisted cubies. 1256. 
conics (Systems of circles determined by a pencil of). 1107. 
CONTACT=PHENOMENA (On the granitic area of Rokan (Middle-Sumatra) and on) in 
the surrounding schists. 1190. 
cOPPER (The allotropy of). II. 60. 
— (Measurements on the specific heat of lead between 14° and 80° K. and of) 
between 15° and 22° K. 894. 
COPPER SULPHATE, Copper chlorid (The system :), potassium sulphate, potassium chlorid 
and water at 30°. 533. 
CORDIERITE and Apophyllite (On the real symmetry of). 430, 
