CnEMISTRY. 427 



irMno:ui,ifTl = l, N = 14.()l, 1=12(1.54, and Mii=55.0 ; F=:1S.94. (Jouru. 

 Prakt. Cbeiu. (2), XXXY, 551.) 



Zinc. — Morse and Burton ndetfrminc tbe atomic weight of zinc by 

 the oxidation of the metal. J 'are distilled zinc was treated with nitric 

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

 was strongly ignited in a muffle. Fifteen sxperiments gave figures rang- 

 ing from Zn=65.001 to Zn=65.119, or in mean, Zn=65.10(jwhen = 15.96. 

 The same method with slight differences of detail had i)reviously been 

 used by Krdmann, and was recently (criticised by IMarignac, who 

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

 also that it retained oxides of nitrogen. Morse and Burton show these 

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



Reynolds and Ramsay 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. 06135, 

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

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



Zinc, iron, and aluminum. — The equivalents of these metals as roughly 

 redetermined by students in his laboratory have been published by J. 

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

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

 when H=l. 



Fifteen experimeuts Zii=:64.95"2. 



Fourteen experimeuts Fe^.^).5.777. 



- Thirteen experiments A1^27.049. 



The values obtained in the individual determinations are not sharply 

 concordant, and the work is chiefly interesting from 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. — Richards has piiblished two papers on the atomic weight of 

 this element. AYheu metallic copper is placed in a solution of silver 

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

 the reaction is sharply quantitative. In the first paper six experiments 

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

 Ag=107.675, we can deduce the value Cu=63.437. In the second paper 

 Richards states that the silver of his 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, Cu =63.450; i .0006. (Proc. Amer. 

 Acad., XXII, 346, aud xxiii, 177.) 



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

 by means of the bromide. That compound 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 



