A Modified Fehling Test and a Modified Corrected Benedict Test William D. Hill, Jr. North Carolina Central University, Durham, NC 27707 The additions of 1L of concentrated sodium hydroxide to comhinations of 32.00 g (0.06 mol) of iron(II1) sulfate nonahydrate, 12.00 g (0.04 mol) of sodium potassium tartrate tetrahydrate, 200mL of distilled water, and a slight excess of the theoretical amount of an aldehyde produced dark solutions that were heated on a hot plate for a 6-min average in which dark red precipitates were formed. The precipitates were subjected to gravitational filtration, washed four times with 1L of distilled water. and given ample time to dry. The black and partially ferrt~magneiicsubstancesproduced were transf~rredto suitable-si7e containers and heated over Runsen burner flames for approximately 12 min and given ample time to cool. These solids remained hlack but were more ferromagnetic and were found to weigh 10.8877 g (99.996% based on iron(II1) sulfate nonahydrate). a-Hydroxy ketones in slight excess of the theoretical amounts were mixed with combinations of 0.06 mol of iron(111) sulfate nonahydrate, 0.04 mol of sodium potassium tartrate tetrahydrate, and 200 mL of distilled water. The rest of the process in which 10.8877 g of hlack ferromagnetic substance was produced was similar to the above process after the additions of 1L of concentrated sodium hydroxide to tht! combinations. The dark red preripitnte~were formed in an averare of fi rnin of heating the dark solutions on a hot plate, and approximately 12 mrn of heating per black solid over a Bunsen burner flame were needed to ferromagnetize completely the hlack solids. T h e additions of 600 mL of concentrated sodium carbonate to comhinations of 0.06 mol of iron(II1) sulfate nonahydrate, 15.00 g (0.051 mol) of sodium citrate dihvdrate. 200 mL of distilled water. and a slight excess of thL..the(mtical amount of an aldehyde and th&dditions of 600 ml, of concentrated sodium carbonate to combinations of 0.06 mol of iron(II1) sulfate nonahydrate, 0.051 mol of sodium citrate dihydrate, 200 mL of distilled water, and a slight excess of the theoretical amount of an a-hydroxy ketone produred fizzings or efl'er\.escences that ceased after a t+w minutpsof heating on a hot plate. The additions of I Lof concentrated sodium hydroxide rausrd dark red precipitates to form, and these materials were heated approximately sixmore minutes. The remainder of the processes in which hlack ferromaenetic solids weiehine .. 10.8877 e were ~ r o duced was similar to the final stages of the abo\,e processes. I t took nu~~n~ximatelv 12 min of heating-. Der black solid over .. a Bunsen burner flame to ferromagnetize these solids completely. All the above reactions were executed to show that iron(111) sulfate supplements copper(I1) sulfate in the oxidation of aldehydes of any type (aliphatic, aromatic, a combination of the two, glutaraldehyde, and a-hydroxy) and a-hydroxy ketones. The equations for these reactions are 0
I
o
X
+ 9Na,SO, + 10H,O + 2Fe304 0
II
RC-H 984
+ 3Fe,(SO,), + Na,C03 + 17NaOH Journal of Chemical Education
+ 9Na,SO, + C0,f + 9H20+ 2Fe,0,
for aliphatic, aromatic, and a combination of aliphatic and aromatic aldehydes, 0
0
11
1
HC-(CH,),CH
Tartrate>
0
II
NaOC-(CH,),CONa 0
A
+ GFe,(SO,), + 38NaOH Na
0
I/
+ 18NaZSO4+ 20H20+ 4Fe,0,
0
II
I/
HC-(CHJ-CH
+ 6Fe2(S0,), + N+CO, 0
0
A
+
II
> NaOC-(CH,),CONa
1I
36Na0H Na Citrate
for glutaraldehyde, 0
I
RCH(0H)C-H
+ GFe,(SO,), + 37NaOH Na
I
A
Tartrate>
/I
+ 35NaOH Na Citrate A >RC-C-ONa
for a-hydroxy aldehydes, and 0
I
RCH(0H)C-R
11 RC-H + 3Fe,(SO,), + 19NaOH Na KTartrate> RC-ONa A
II > RC-ONa
A
Na Citrate
+ 3Fe2(SO,), + 18NaOH 0 0
X
A
Na K Tartrate'
I/ 11
RC--C-R
+ 9NazS0, + 10H,O + 2Fe,0,
