SYNTHESIS OF COPPER(I1) SULFIDE A'ubrnttted by: Roderich Scheer, \T~aldoberschule(Gymnasium), Charlottenburg, West Berlin C'h~cked bu: Imwi .J. LI~llerand Joseph 1, Clouser. Main Tonn?hip High School, l'laines, Illmois
PREPARATION
Provide 12.8 g copper powder, (i.4 g powdered sulfur (stoichinmetric quantities), 200 ml of copper(11) sulfate snlut,ion, and a 400 ml tmtkw \vit,h a hurner or hot, plate. DEMONSTRATION
Mix thc copper and sulfur powless and add to the copper sulfate solut,iom Stir and heat to boiling. After a few minntes black CuS \ d l he seen mixed with t,he sulfur. The mixture will thicken and shortly
5ettle out indicatmg the end of th? reaction, Filter and dry the product a t room temperature REMARKS
I t may he shomn by the use of a mmoscope that the product is uniform Students may be asked to analyze the product by heating a weighed ample, recording the loss m veight, and calculating the combining proportions The copper sulfate solution serves a5 a catalyst, and no change in w i g h t of copper wlfate occurs as a rewlt of the reaction.
( (
MAGNETIC SUSCEPTIBILITIES-lRON(l1)
ION
Submdted bg: Carl W,lloeller, University ot Chnecticut, Storrs Checked b11: Charles .I. Root, The Ohio State 17iiiver?ity, Columb115 i
PREPARATION l'rovidc a t,riple 11eam halance of sensitivity of
0.01 g, a n1:ignct xitli field strength of approximately ,5000 oerstcxis, and Pywx tubing sealed a t one end, dimensi6ns 20 mi long and 10 mm i d , Seal t,wo small glass hooks to t,he lip of the tub? and at,ta,eh to these a piece of coppcr r i r c t,o suspend the t,ube from the hook of the halaxire aft,er re~novi~lg the pail and panholder. l+eparc the solutions: (a) I0 g FcCl2~41Mlin 100 ml distilld ~ x t t e(0.31) ~ and (bj 21 g K4Fe(CY)6.:3Hs0 iri 100 lnl dist,illd ~ n i t c r(0.5M). DEMONSTRATION I'our I 0 mi of iron(I1) chloride sohtion into t,he tube
and halance d h thc nlagnpt, removed. Then adjust thr magnet, so that t,hc, top of the liquid is centered h e t ~ w mt,he poles :md agaili balanre. The sample will w i g h less in the 1nagrii4c field sinw the paramagnetic
sample is pulled up into the field. Rinse the t,ube with distilled water and repeat t,he weighings with 10 ml of the K4Fe(CK)8solution in the tube. This diamagnetic sample will weigh more in the magnetic field. The unpaired electrons of the iron(f1) ion h a m hem paired in the ferrocyanate mmplex ion. REMARKS
The weigl~ingsmaybe repeated with 10 ml of distilled ~vaterin the tube ta demonstrate t,he relatively small effect of the diamagnetic solvent. 1%r demonstrating to large groups, the eEect of applying and removing the magnetic field can be magnified by attaching a small mirror to the balanw arm and reflecting light from this tc~a screen. The checker noted some apparent loss in weight 11sing 1
