Edited by GEORGEWlGER California State University
textbook forum The Crystal Field Stabilization Energy (CFSE) Swarn Singh Parmar Guru Nanak Dev Universily Amritsar, India Only a few of the compr~hensivetexthooks 01 inorganic chemistrv or(nide an adequate discussion of thc crystal field stabiliza%n energy (CFSE), an important parameter of transition metal complexes, in terms of the strength of the crystal field (10 D,)and the mean pairing energy (P). Several texts disagree on the value of the CFSE for octahedral complexes of d6 to dlo metal ions in both the weak and strong crystal fields. Accordine to Dav and Selbin' CFSE is the eain in enerw achieved by-the prlfeferential filling of the lowehying d lev& over the enerw of a comoletelv random occuoancv . - of all five d levels. ~ccl;dingly *
CFSE =Em,-E = E m , - n S
(1)
Where E is the energy of the random filling, which is zero in the absence of anv and nqP for nl electron oairs in "oairine . random filling, and Emt is b e ener& of thebreferentih filling of the lower-lying d orbitals. If there are n l pairs in the preferential filling and x and y are the number of electrons in t2, and e, orbitals, respectively,
E,, = (-4x
+ 6 y ) Dq+ nlP
and eqn. (1)can be written as
+ (nl- ndP (2) The CFSE values obtained from eans. . (1) . . and (2) . . are the same CFSE = (-4x
+ 6y)D,
as given by Day and Selhin. Values given elsewhere are in error because either En,+ values have been mistaken for CFSE values, even for dx to dlo cases, or P has been totally ignored.
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Day, Jr., M. C.. and Selbin. J., "Theoretical Inorganic Chemistry." 2nd Ed.. Affiliated East-West Press Pvt-Ltd.. East-West Student Ed..
A Practical Solvay Process Experiment J. R. McKee J. M. Kauffman Phi adelpn a College d Pharmacy and Science 43rd Slreet and < ngsesr ng Mal. Pn ladelpn a. PA I9104
The Solvay synthesis of sodium hydrogen carbonate has become less popular in recent years,' partly, we suspect, because of the difficulty in obtaining any product within a reasonable length laboratory period. In order to speed up the process, we decided to use an initial reaction mixture containine. in addition to the usual sodium chloride and ammonia,2 sodium bicarbonate in about the amount found in Solvay process liquor after ~ e a c t i o nThis . ~ mixture may be prepared beforehand and filtered. Students may be told that it represents an industrial mixture that is to be recycled. Knowing that the liquid is 25% sodium chloride by weight, students may weigh it into the reaction vessel and can base their yield cal-
Carson, CA 90747
f-, Ex~erimentalset-uo,a. thistle tube. .oolvethvlene. . . Nalae 6210. with stem from sacom &he as enensoon b, ruober stoppers: c. 250-rn~ Florence flasr,d, glass hbng: e. homr 1-0 ng: 1.400ml bone: g. medmnedroppn *m lmmapening. h. 50-ml conical flask: i,thermometer (optional). culations on sodium chloride as the limiting reagent. Bubbling carbon dioxide into this mixture for about 45 min reliably caused a precipitate of sodium bicarbonate to appear, and another 30 min gave a usable amount. T h e experiment, which illustrates the generation and purification of a gaseous reactant, can be completed in 2-2lI.2 hours if damp product is acceptable. Sodium Hydrogn Carbonate Calcium carhonate,4 55 g (0.55 mole), was weighed into a 250-ml Florence flask and covered with 20 ml of water. The aooaratus was .. maembled nr hhown in the tigurr wlth water in thr 100-mlwash hottle ond the rarbcn dwxide outlet exit:ny to the atmosphere at tirst. Abut 111 ml uf 6 A1 hgdrurhluric acids wns added to the carbon dimide generator and allowed to react in order to sweep air out of the system and to cheek its operation. The carbon dioxide outlet, a medicine dropper with -1-mm opening, was then placed into a 50-ml conical flask containing 53.9 g (or 46.0 ml) of Solvay Process Recycle Liquid6 and a thermometer. Additional hvdrochloric acid was added in 510-mlportions ta the carbon dioxide generator to maintain a flow rate of 2 4 mllsee, best viewed in the wash bottle. White solid sodium hydrogen carbonate appeared in 45 min, and the rate of formation seemed linear with time. Reaction was halted arbitrarily after a total of 1.25 hr, and the product was suction filtered with a 5.5-cm B"chner, washed with 20 ml of 50%ethanol, and suctioned "dry" for 5 min7 to yield 2.7 g (13%)
' Kiiksey. H. G., J. CHEM. Eouc. 55,272 (1978).
Hered, G. R., Nebergall, W. H., and Hered, W.. "Basic Laboratoty Studies in College Chemistry," 6th Ed., D. C. Heath 8 Co., Lexington, MA, 1980, pp. 291-293. Thorpe. J. F.. and Whiteley, M. A.. "Thorpe's Dictionary of Applied Chemistry." Supplement, Vol. 11,Longmans. Green & Co.,London, 1935, pp. 369-370. Used marble chips of 0.5 om3, Fisher M-123. 200 ml is required on this scale. Previously made from 205 g of NaCI, 55 g of NaHC08.240 ml of 28% NH3. and 360 ml of water magnetically stirred overnight in a rubber-stoppered. 1-1 conical flask, then filtered by gravity. It contains 25% NaCl wlw, and its density is 1.17 glml at 25OC. Halitem brand of rock salt seemed to wwk better than reagent grade NaCl and cost much less. Drying "reduced" the yield to 1.8 g (9%).
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Volume 58
Number 12
December 1981
1035
