- Email: [email protected]
New titrimetric microdetermination of glycols
hllCROCHEh1
LrAL
New
Titrimetric \-.
Cizrmiral
12,
JOURSiZL
N\;. 1’.
Lahornforirs,
435-439
(1967)
Microdetermination $hUVASTAV.A
AIVD
l:niversiiy Rrwiwd
0.
of c‘.
of .lllahnbad, March
Glycols
SAXENA
Allahabad,
India
21, 1967
INTKODUCTIOS
Literature concerning the volumetric estimation of glycols is rather sparse. Redrinskii and Skornyakova (1) attempted to determine ethylene glycol and propylene glycol by oxidizing with potassium dichromate. Schaefer (2) determined glycol in dilute solutions containing oxidizable impurities where they calculated the results by assumingthat the reaction goesonly to 97.97&. Cannon and Jackson (3) determined small amounts of 1,2-propylene glycol in ethylene glycol by oxidizing with periodic acid, and removed the aldehydes by distillation. Charles and Hatch (4) determined 1,2-propylene glycol in ethylene glycol mixtures with silver nitrate. (‘ardone and Compton (5) suggested the determination of diethylene glycol by oxidation with potassium dichromate. Hess and co-workers (6) developed a method based on the fact that AgIOR is nearly insoluble in dilute nitric acid whereas Ag104 is soluble. Wurist and Firsova (7) determined ethylene glycol by acetylating and back titrating the remaining NaOH with acid. The present method dealswith the determination of glycols by oxidation with gold chloride in the presence of excessalkali. A known excess of gold chloride is added to either a solution of ethylene glycol, 1,2-propylene glycol, or trimethylene glycol in the presenceof a large excessof sodium hydroxide; this is heated for three hours on a hot plate (the reaction mixture should not be allowed to evaporatej. The gold chloride solution is reduced to metallic gold corresponding to the glycol oxidized. Probably the following reactions occur between gold chloride and glycols in alkaline media:
436
V.
N.
P.
SRIVASTAVA
AND
0.
C.
SAXENA
4
rHZoH
+ 4AuCla + 12NaOH + 8HCHO
$4Au + 12NaCl + IOH + O2
+ 4AuCla + 12NaOH + 4HCH0 + 4Au + 12NaClf
+ 4CHsCHO lOH20 + 02
+ 4AuCla + 12NaOH + 4HCH0 + 4Au + 12NaCl+
+ 4CH:KHO lOH20 + 02
CHzOH 4
LH 2
In the case of ethylene glycol only formaldehyde (8) is formed during its oxidation as it gives a positive test with sodium nitroprusside. The remaining gold chloride is estimated (9) by acidifying the solution and titrating back by adding known excess of potassium ferrocyanide against a standard solution of ceric sulphate using N-phenyl anthranilic acid as indicator. The results agree with those obtained by a standard method (10); similar and precise values were found. EXPERIMENTAL
Chemicals
Employed
Gold chloride (Palmston’s grade sample) ; ethylene glycol (B.D.H. grade sample) ; 1,2-propylene glycol (B.D.H. grade sample) ; trimethylene glycol (B.D.H. grade sample) ; sodium hydroxide (Merck, grade sample) ; potassium ferrocyanide (B.D.H. AnalaR, grade sample) ; sulphuric acid B.D.H. (AnalaR B.D.H. grade sample) ; ceric sulphate (Technical AnalaR grade sample) ; grade sample) ; sodium carbonate (B.D.H. N-phenyl-anthranilic acid (B.D.H. grade sample) ; and ferrous ammonium sulphate (B.D.H. AnalaR grade sample). A ceric sulphate (in 8N H&O*) solution is standardized against a standard solution of ferrous ammonium sulphate (in 1N H$SOh) using N-phenyl-anthranilic acid as indicator.
PROCEDURE
Since the method is the same for the determination of either ethylene 1,2-propylene glycol, or trimethylene glycol, only glycol will be mentioned in the following procedure: To a solution of glycol, a known excess of a standard solution of gold chloride is added. Thereafter the reaction mixture is treated with an excess of sodium hydroxide (standard) solution and kept on a hot plate for three hours. After cooling the reaction mixture to room temperature, the metallic gold is filtered and washed thoroughly with distilled water. The filtrate and the washings are collected. acidified, and titrated back by adding a known excess of a standard solution of potassium ferrocyanide against a standard solution of ceric sulphate using S-phenylanthranilic acid as an indicator. A brownish red color appears sharply at the end point. glycol.
RESL-LTS
The results of determinations on the three compounds are shown in Tables 1-3. Ranges in which ethylene glycol, 1,2-propylene glycol, and trimethylene glycol have been estimated vary from 0.1294 to 0.6365 mg; 0.6348-3.147 mg:; and 0.5289-2.615 mg. respectively.
This paper has described a new method for the microdetermination oi glycols. This was done by an oxidation-reduction reaction in which gold chloride in an alkaline medium was used to reduce a glycol. The method gives accurate results if TABLE DETERMINATION
Amounts Ethylene plycol
1
OF ETHYLENE
Gr.~co~
used Ethylene ~l\-col (found)
NaOH
AUCI,
0.0104121
O&V
0.0162:Y
0.0391.1’
0.0087Y
0.0087Iv
(ml)
(ml)
(ml) -
(ml)
(ml)
(ml)
(mx)
25 2.5 2 .5 25 2s 2.5 25
11.24 7.90 8.14 8.36 8.60 8.86 9.08
3.34 0.24 0.46 0.70 0.96 1.18
0.1294 0.2481 0.3776 0.6178 0.6365
0.2 0.4 0.6 0.8 1 .o
25 25 25 25 25
2 2 2 2 2 2
K4Fe(CN),;
Ce(SO,),
WSO,),
438
V.
N.
P.
SRIVASTAVA
AND
TABLE DETERMINATION
NaOH
0.0417&f (ml)
O.SAr (ml)
AuCI,
0.0391,~ (ml)
Ce(S0J2 0.0087A’ (ml)
0.6348
6.52
1.96
1.2960
7.42 8.46
2.86 3.90
1.8910 2.5780
9.32
4.76
3.1470
11.24
2.5 2.5
4.56 5.52
0.4
25
4
2.5
0.6 0.8
25 25
4 4
2.5 2.5
1.0
25
4
2.5
0.0348M
(ml)
-
3
OF TRIMETHYLENE
Amounts
0.0087N (4
1,2-Propylene glycol (found) (w) -
2.5 4 4
TABLE
CeG04)2
-
25
Trimethylene glycol
GLYCOL
6.68 0.96
0.2
DETERMINATION
SAXENA
used
K,Fe(CN16
0.0162N (ml)
C.
2
OF 1,2-PROPYLENE
.4mounts 1,2-Propylene glycol
0.
GLYCOL
used
NaOH
AUCI,,
K,Fe(CN),
Ce(S04)s
0.8N (ml)
0.01625
0.03915
0.0087N
(ml)
(ml)
(ml)
(ml)
11.24 4.56
WSO,)~ 0.00871V
Trimethylene glycol (found) (wd
-
-
4
2.5 2.5
6.68
-
0.2 0.4
25 25
4 4
2.5 2.5
5.36 6.12
0.80 1.56
0.5289
0.6
25
4
2.5
6.94
2.38
1.03 10 1.5730
0.8 1.0
25 25
4 4
2.5 2.5
7.72 8.52
3.16 3.96
2.0890 2.6180
glycols are present in traces. This method is unique in that the reaction proceeds to one step only, i.e., to the formation of aldehydes. The reaction between gold chloride and glycol takes place in the ratio of 1: 1. ACKNOWLEDGMENT Dr. The authors are grateful to Dr. Bal Krishna, Srivastava; and to the University Grant Commission India) for providing financial assistance.
M. P. Singh and C.S.I.R.
and Dr. M. (Government
N. of
REFERENCES I.
KEDRINSKII,
propylene Cracking 205
(1935).
V. V., AND SKORNYAKOVA, V. F., Determination of ethylene and glycol by oxidation with potassium dichromate. Materials on and Chemical Treatment of Products Obtained. Khimteoret. 2, 201-
hIICKOL)ETERMINATION 2. Sc~r,zwen, 3. i. S. 6. 7. K. Y. 10.
OF GLYCOLS
439
in dilute solutions WILLIAM E., Determination of glycol or glycerol .1xaZ. Ed. 9, 449-350 (1937). containing oxidizable impurities. Ixd. Eng. Chm., CANSON, \V. A., .4x11 JA~SON, L. C., Determination of small amount oi 1,2propylene in ethylene plycol. .A&. Chrm. 24, lOi.i-10.53 ( 1952). JORUO_\J, CIIARLES B., .wn HAXIT, \‘IIKXI. 0.. Dctcrmimttion of I,?-props lrnc gl~-co1 in eth>lenc glycol mixtures. Annl. Chrm. 25, 636-6.18 (1953i. CAR~ONI:. MARW J., AND CO~IPRK, JOIIS \V., Dichromnte oxidation ni diethylcne glycol. Anal. Chrlla. 25, 1869.liii4 (195.1). I~ESS, EI.LES K., JOKDOK, CIIAKIXS H.. ANI) Ross, HAI.xI,.~ I<., Tktermin;ltion of ethylene glycol in water. ~~I&. Chem. 28, l.il-13.7 (1956). PURIST, I. M., AND FIRSOVA, Uu. F., Iktermination of ethhlcnc glycol and its mono&h>-1 ethers. Zh. .Innlif. Khini. 11. 205-207 (1950). CLAKKK, Hnn-s Trr~cwx, A Hand Kook ci (irranic .\nal?sis~~Qu;llitati\-r and C)u;rntitative.” p. 127 (1956). S~XF.KA, 0. C., A new volumetric method ior thr estimntion of Gold. Z~rdinrz /. .lppl. Chfm. 1, 1071 (1966). SIIUPE, 1. S., Periodate reaction :Ipp!ird to cosmetic ingrcdicnts. Tktermination of glycerol, cthvlcnc plycol. and prop> lent #Iyc!)l. J. .1.\.\oc-. o&fir. .lgr. (‘hrmists 26, 249 (1943) :
LrAL
New
Titrimetric \-.
Cizrmiral
12,
JOURSiZL
N\;. 1’.
Lahornforirs,
435-439
(1967)
Microdetermination $hUVASTAV.A
AIVD
l:niversiiy Rrwiwd
0.
of c‘.
of .lllahnbad, March
Glycols
SAXENA
Allahabad,
India
21, 1967
INTKODUCTIOS
Literature concerning the volumetric estimation of glycols is rather sparse. Redrinskii and Skornyakova (1) attempted to determine ethylene glycol and propylene glycol by oxidizing with potassium dichromate. Schaefer (2) determined glycol in dilute solutions containing oxidizable impurities where they calculated the results by assumingthat the reaction goesonly to 97.97&. Cannon and Jackson (3) determined small amounts of 1,2-propylene glycol in ethylene glycol by oxidizing with periodic acid, and removed the aldehydes by distillation. Charles and Hatch (4) determined 1,2-propylene glycol in ethylene glycol mixtures with silver nitrate. (‘ardone and Compton (5) suggested the determination of diethylene glycol by oxidation with potassium dichromate. Hess and co-workers (6) developed a method based on the fact that AgIOR is nearly insoluble in dilute nitric acid whereas Ag104 is soluble. Wurist and Firsova (7) determined ethylene glycol by acetylating and back titrating the remaining NaOH with acid. The present method dealswith the determination of glycols by oxidation with gold chloride in the presence of excessalkali. A known excess of gold chloride is added to either a solution of ethylene glycol, 1,2-propylene glycol, or trimethylene glycol in the presenceof a large excessof sodium hydroxide; this is heated for three hours on a hot plate (the reaction mixture should not be allowed to evaporatej. The gold chloride solution is reduced to metallic gold corresponding to the glycol oxidized. Probably the following reactions occur between gold chloride and glycols in alkaline media:
436
V.
N.
P.
SRIVASTAVA
AND
0.
C.
SAXENA
4
rHZoH
+ 4AuCla + 12NaOH + 8HCHO
$4Au + 12NaCl + IOH + O2
+ 4AuCla + 12NaOH + 4HCH0 + 4Au + 12NaClf
+ 4CHsCHO lOH20 + 02
+ 4AuCla + 12NaOH + 4HCH0 + 4Au + 12NaCl+
+ 4CH:KHO lOH20 + 02
CHzOH 4
LH 2
In the case of ethylene glycol only formaldehyde (8) is formed during its oxidation as it gives a positive test with sodium nitroprusside. The remaining gold chloride is estimated (9) by acidifying the solution and titrating back by adding known excess of potassium ferrocyanide against a standard solution of ceric sulphate using N-phenyl anthranilic acid as indicator. The results agree with those obtained by a standard method (10); similar and precise values were found. EXPERIMENTAL
Chemicals
Employed
Gold chloride (Palmston’s grade sample) ; ethylene glycol (B.D.H. grade sample) ; 1,2-propylene glycol (B.D.H. grade sample) ; trimethylene glycol (B.D.H. grade sample) ; sodium hydroxide (Merck, grade sample) ; potassium ferrocyanide (B.D.H. AnalaR, grade sample) ; sulphuric acid B.D.H. (AnalaR B.D.H. grade sample) ; ceric sulphate (Technical AnalaR grade sample) ; grade sample) ; sodium carbonate (B.D.H. N-phenyl-anthranilic acid (B.D.H. grade sample) ; and ferrous ammonium sulphate (B.D.H. AnalaR grade sample). A ceric sulphate (in 8N H&O*) solution is standardized against a standard solution of ferrous ammonium sulphate (in 1N H$SOh) using N-phenyl-anthranilic acid as indicator.
PROCEDURE
Since the method is the same for the determination of either ethylene 1,2-propylene glycol, or trimethylene glycol, only glycol will be mentioned in the following procedure: To a solution of glycol, a known excess of a standard solution of gold chloride is added. Thereafter the reaction mixture is treated with an excess of sodium hydroxide (standard) solution and kept on a hot plate for three hours. After cooling the reaction mixture to room temperature, the metallic gold is filtered and washed thoroughly with distilled water. The filtrate and the washings are collected. acidified, and titrated back by adding a known excess of a standard solution of potassium ferrocyanide against a standard solution of ceric sulphate using S-phenylanthranilic acid as an indicator. A brownish red color appears sharply at the end point. glycol.
RESL-LTS
The results of determinations on the three compounds are shown in Tables 1-3. Ranges in which ethylene glycol, 1,2-propylene glycol, and trimethylene glycol have been estimated vary from 0.1294 to 0.6365 mg; 0.6348-3.147 mg:; and 0.5289-2.615 mg. respectively.
This paper has described a new method for the microdetermination oi glycols. This was done by an oxidation-reduction reaction in which gold chloride in an alkaline medium was used to reduce a glycol. The method gives accurate results if TABLE DETERMINATION
Amounts Ethylene plycol
1
OF ETHYLENE
Gr.~co~
used Ethylene ~l\-col (found)
NaOH
AUCI,
0.0104121
O&V
0.0162:Y
0.0391.1’
0.0087Y
0.0087Iv
(ml)
(ml)
(ml) -
(ml)
(ml)
(ml)
(mx)
25 2.5 2 .5 25 2s 2.5 25
11.24 7.90 8.14 8.36 8.60 8.86 9.08
3.34 0.24 0.46 0.70 0.96 1.18
0.1294 0.2481 0.3776 0.6178 0.6365
0.2 0.4 0.6 0.8 1 .o
25 25 25 25 25
2 2 2 2 2 2
K4Fe(CN),;
Ce(SO,),
WSO,),
438
V.
N.
P.
SRIVASTAVA
AND
TABLE DETERMINATION
NaOH
0.0417&f (ml)
O.SAr (ml)
AuCI,
0.0391,~ (ml)
Ce(S0J2 0.0087A’ (ml)
0.6348
6.52
1.96
1.2960
7.42 8.46
2.86 3.90
1.8910 2.5780
9.32
4.76
3.1470
11.24
2.5 2.5
4.56 5.52
0.4
25
4
2.5
0.6 0.8
25 25
4 4
2.5 2.5
1.0
25
4
2.5
0.0348M
(ml)
-
3
OF TRIMETHYLENE
Amounts
0.0087N (4
1,2-Propylene glycol (found) (w) -
2.5 4 4
TABLE
CeG04)2
-
25
Trimethylene glycol
GLYCOL
6.68 0.96
0.2
DETERMINATION
SAXENA
used
K,Fe(CN16
0.0162N (ml)
C.
2
OF 1,2-PROPYLENE
.4mounts 1,2-Propylene glycol
0.
GLYCOL
used
NaOH
AUCI,,
K,Fe(CN),
Ce(S04)s
0.8N (ml)
0.01625
0.03915
0.0087N
(ml)
(ml)
(ml)
(ml)
11.24 4.56
WSO,)~ 0.00871V
Trimethylene glycol (found) (wd
-
-
4
2.5 2.5
6.68
-
0.2 0.4
25 25
4 4
2.5 2.5
5.36 6.12
0.80 1.56
0.5289
0.6
25
4
2.5
6.94
2.38
1.03 10 1.5730
0.8 1.0
25 25
4 4
2.5 2.5
7.72 8.52
3.16 3.96
2.0890 2.6180
glycols are present in traces. This method is unique in that the reaction proceeds to one step only, i.e., to the formation of aldehydes. The reaction between gold chloride and glycol takes place in the ratio of 1: 1. ACKNOWLEDGMENT Dr. The authors are grateful to Dr. Bal Krishna, Srivastava; and to the University Grant Commission India) for providing financial assistance.
M. P. Singh and C.S.I.R.
and Dr. M. (Government
N. of
REFERENCES I.
KEDRINSKII,
propylene Cracking 205
(1935).
V. V., AND SKORNYAKOVA, V. F., Determination of ethylene and glycol by oxidation with potassium dichromate. Materials on and Chemical Treatment of Products Obtained. Khimteoret. 2, 201-
hIICKOL)ETERMINATION 2. Sc~r,zwen, 3. i. S. 6. 7. K. Y. 10.
OF GLYCOLS
439
in dilute solutions WILLIAM E., Determination of glycol or glycerol .1xaZ. Ed. 9, 449-350 (1937). containing oxidizable impurities. Ixd. Eng. Chm., CANSON, \V. A., .4x11 JA~SON, L. C., Determination of small amount oi 1,2propylene in ethylene plycol. .A&. Chrm. 24, lOi.i-10.53 ( 1952). JORUO_\J, CIIARLES B., .wn HAXIT, \‘IIKXI. 0.. Dctcrmimttion of I,?-props lrnc gl~-co1 in eth>lenc glycol mixtures. Annl. Chrm. 25, 636-6.18 (1953i. CAR~ONI:. MARW J., AND CO~IPRK, JOIIS \V., Dichromnte oxidation ni diethylcne glycol. Anal. Chrlla. 25, 1869.liii4 (195.1). I~ESS, EI.LES K., JOKDOK, CIIAKIXS H.. ANI) Ross, HAI.xI,.~ I<., Tktermin;ltion of ethylene glycol in water. ~~I&. Chem. 28, l.il-13.7 (1956). PURIST, I. M., AND FIRSOVA, Uu. F., Iktermination of ethhlcnc glycol and its mono&h>-1 ethers. Zh. .Innlif. Khini. 11. 205-207 (1950). CLAKKK, Hnn-s Trr~cwx, A Hand Kook ci (irranic .\nal?sis~~Qu;llitati\-r and C)u;rntitative.” p. 127 (1956). S~XF.KA, 0. C., A new volumetric method ior thr estimntion of Gold. Z~rdinrz /. .lppl. Chfm. 1, 1071 (1966). SIIUPE, 1. S., Periodate reaction :Ipp!ird to cosmetic ingrcdicnts. Tktermination of glycerol, cthvlcnc plycol. and prop> lent #Iyc!)l. J. .1.\.\oc-. o&fir. .lgr. (‘hrmists 26, 249 (1943) :