CnEMlSTRY. 427 



iiiiiu'aii,il 1U=I, N = 14.01,T = JL>().r)l, aii(lMii=55.0; F=18.04. (.Joiini. 

 Frakt. Choiii. (2), xxxv, 551.) 



Zinc. — l\r<)isc and P>urt(ni rcdolrrminc the atomic ucighl of zinc by 

 the oxidation of tlic metal. Tuie distilled zinc was treated with nitric 

 acid, and the residue from the evaporated solution after gentle heating 

 was strongly ignited in a muflle. Fifteen ?xperinients gave figures rang- 

 ing from Zn =05.091 to Zn =05.119, or in mean, Zn=(J5.10Gwhen 0= 15,90. 

 The same method witli slight differences of detail had previously been 

 used by Erdmann, an<I was recently criticised by Marignac, who 

 claimed that oxide of zinc was dissociated at high temperatures, and 

 also that it retained oxides of nitrogen. Morse and ]>urton show these 

 objections to be groundless. (Am. Chem. Journ., x, 311.) 



Reynolds and Kamsay estimate, with many elaborate precautions, 

 the amount of hydrogen evolved upon the solution of pure zinc in an 

 acid. Twenty-nine experiments were made, of which twenty-four were 

 rejected. The remaining five when fully corrected give concordant 

 values, making the atomic weight of zinc in mean, Zn = 05.4787, i .00135. 

 The weight of the hydrogen measured was computed by means of Eeg- 

 nault'sdata. (Jouru. Chem. Soc, December, 1887.) 



Zinc, iron, and aliiminnm. — The equivalents of tliese metals as roughly 

 redetermined by students in his laboratory have been i)ublished by J. 

 Torrey, jr. In each case the metal was dissolved in an acid, and the 

 liydrogen set free was measured. The mean results are as follows, 

 when H=l. 



Fifteen experiments Zu=(J4.95'2. 



Fourteen experinieuts b e^^f).???. 



Thirteen experiments Al='27.049. 



The values obtaine<l in the individual determiiuitions are not sharply 

 concordant, and the work is chiefly interesting froiu the stand-point of 

 the teacher. It illustrates the possibility of training students in the 

 verification of important constants. (Am. Chem. Journ., x, 73.) 



Copper. — Kichards has published two papers on the atomic weight of 

 this element. When metallic copper is i)laced in a solution of silver 

 nitrate, metallic silver is precipitated, and when the solution is ice cold 

 the reaction is shai])ly (piantitative. In the first paper six experiments 

 are given, in whic^li the silver was dried at 150° C. From them, if 

 Ag=107.C75, we can deduce the value Cu =03.437. In the second paper 

 Kichards states that the silver of liis earlier series of weighing still re- 

 tained traces of moisture. Five additional determinations were there- 

 fore made, in which the silver before weighing was heated to incipient 

 redness. These gave in mean, ('n = 03.450: rl^ .0000. (Froc. Amer. 

 Acad., XXII, 340, and xxiii, 177.) 



tSilicoii. — Thorpe and Young re-determine the atomic weight of silicon 

 by means of th«^ bromide. That com[)()und was decomposed by water, 

 and after evaporation to dryness the residual silica was weighed. 

 Nine experiments were made, giving from Si = 28.243 to Si = 28.429 ; in 



