Chemistry and Physics. 497 



protection at all from the action of sunlight upon the iodide of 

 starch. Further experiments showed that the action of X-rays 

 upon this substance gave the same effect as sunlight. — Cumptes 

 liendvs, clxiii, 205, 29:}. H. L. w. 



3. The Crystallization of Calcium Tartrate. — Few salts have 

 been more frequently prepared than calcium tartrate, on account 

 of its employment for the recognition of the acid, and it is sur- 

 prising to find that little is known of its behavior when crystal- 

 lizing from aqueous solution. It has been observed by F. D. 

 Chattaway, of Oxford University, that when equal volumes of 

 0-2 A r solutions of calcium chloride and potassium sodium tartrate 

 are mixed at ordinary temperature the liquid remains clear for a 

 short time, then small tufts of needle-shaped crystals make their 

 appearance and rapidly grow until in a few minutes the whole is 

 tilled with such tufts, which finally interlace, producing a felted 

 mass of crystals to such an extent that the vessel may be inverted 

 without loss of mother-liquor. This salt is the hexahydrate, 

 CaC 4 H 4 6 .6lI 3 0. This form is unstable, and after a short time at 

 ordinary temperature small orthorhombic crystals of the tetra- 

 hydrate, CaC 4 H 4 6 .4H 2 0, make their appearance and grow 

 rapidlv, settling to the bottom of the liquid, while the needle- 

 shaped crystals dissolve and disappear. The change takes place 

 more rapidly when the mass is stirred or shaken vigorously, and 

 it. is still more rapid upon heating. This phenomenon should 

 furnish a striking lecture experiment. — Jour. Amer. Chem. JSoc, 

 xxxviii, 2519. H. l. w. 



4. The Basic Copper Sulphates. — S. W. Young and A. E. 

 Steaen, observing that the results of the analyses of the mineral 

 brochantite, a basic copper sulphate, vary widely, and that a very 

 large number of artificial products have been described which 

 vary between the limits H)CuO.S0 3 and 2CuO.SO s , with vary- 

 ing amounts of water, have made an investigation upon the sub- 

 ject. By treating finely divided copper oxide in closed bottles 

 in a thermostat they obtained some products which appeared to 

 be crystalline, but could not be shown to be homogeneous by 

 microscopic examination. No definite chemical formula was 

 indicated except perhaps in the cases where two molecules of 

 copper oxide were used with one of copper sulphate, and where 

 practically all of the copper sulphate was removed from the 

 solution, a composition corresponding nearly to the formula 

 3CuO.S0 3 .2H 2 was found. The authors believe that no more 

 basic salt than this can be formed under the conditions of their 

 experiments, which were made at 25°, 37\5 and 50° with the 

 same results at all the temperatures. In the cases where less 

 than 2 molecules of copper oxide were used for one of copper 

 sulphate there was only a moderate but gradual change in com- 

 position, reaching about 2-3 CuO, S0 3 .2-4H,0 where \ molecule 

 of copper oxide was used. Although the authors do not suggest 

 it, it appears probable that these are mixtures of two basic 

 sulphates and it is to be hoped that they will continue their 



