Correspondence SUPPLEMENTARY DIRECTIONS FOR PREPARING SOLUTIONS FOR DEMONSTRATION OF CHANGES IN IONIC EQUILIBRIA DURING CHEMICAL REACTIONS
In the November, 1930, issue of the JOURNAL OF CHEMICAL EDUCATION appeared an article by Hosmer W. Stone* describing a demonstration experiment to illustrate ionic equilibria during chemical reactions. Those teachers of high-school chemistry who would like to perform that experiment, but find i t a tedious and long performance to obtain the desired concentration of the solutions, following the directions given by Mr. Stone, will probably find the following table useful. The solutions indicated in this table do not give perfect results, but are satisfactory for classroom demonstration. They may be prepared with little difficulty and very quickly. I use an ordinary medicine dropper to measure the drops. Of course, I need not point out that for the best results it is imperative to use distilled water. Following the directions of this table my students in first-year chemistry have successfully prepared these solutions.
TABLE
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NaCOHHfC1- 4 Na+CIH.0 Reaction No. I BaSO, 2H.O ~eactionNo.I1 Ba++20H- 2H+SO,--+ HAC d NH,+ACHnO NH'OH Reaction No. I11 carl lion No.
Solulion Ne~ersaw
O~dinoryLab. Molerialr
U. S. P. Sticks
I
NaOH
I
HCI
I1
Ba(0H)s
Pure crystals
11 111 111
Ha01 NH,OH HAc*
94.=5.6% H2SOa 2%29%NHa 30% HAc
'
35.4-37.5% HC1
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Dircnionr for Prc9orinp Solulionr
Solution A: 1gramto 100cc. H 2 0 Of solution A add 50 d r o ~ sto 150 cc. H*O Solution A: 5cc.acidto50cc.H20. Of solution A add 25 drops to 150 cc. H20 Solution A: saturate solution at 20°C. and filter. Of solution A add 20 cc. to 140 cc. HsO 9 drops to 150 cc. H.0 6 dmps to 150 cc. HsO 6 drops to 150 cc. H1O
