9.3 Xc nh mu sc ca dung dch

 

Vic xc nh mu sc ca dung dch trong phm vi nu - vng - c tin hnh theo mt trong hai phng php di y, tu theo ch dn trong chuyn lun. Mt dung dch c coi l khng mu nu n ging nh nc ct hay dung mi dng pha dung dch , hoc c mu khng thm hn dung dch mu i chiu N9.

 

Phng php 1

Dng nhng ng thy tinh trung tnh, khng mu, trong sut v ging ht nhau, c ng knh ngoi 12 mm so snh 2,0 ml dung dch th vi 2,0 ml nc ct, hoc dung mi, hoc dung dch mu i chiu (Bng 2a ti 2e) theo ch dn trong chuyn lun. Quan st mu ca dung dch dc theo trc ng, di nh sng khuch tn, trn nn trng.

 

Phng php 2

Dng nhng ng thy tinh trung tnh, y bng, khng mu, trong sut, ging ht nhau v c ng knh trong t 15 - 25 mm so snh lp dung dch th c b dy 40 mm vi lp cht lng c b dy 40 mm ca nc ct, hoc dung mi, hoc dung dch mu chun (Bng 9.3.2a ti 9.3.2e) theo ch dn trong chuyn lun. Quan st mu ca dung dch dc theo trc ng, di nh sng khuch tn trn nn trng.

 

Pha ch cc dung dch gc

Dung mi A: 25 ml acid hydrocloric (TT) ho tan vo 975 ml nc ct.

Dung dch gc mu vng: Ho tan 46 g st (III) clorid (TT) trong dung mi A cho va 1000 ml. Chun ri iu chnh bng dung mi A c dung dch cha 45 mg FeCl3. 6H2O trong 1 ml. Bo qun trnh nh sng.

Chun : Cho vo mt bnh nn dung tch 250 ml c nt mi 10 ml dung dch mu vng, 15 ml nc, 5 ml acid hydrocloric (TT) v 4 g kali iodid (TT). Lc u ri yn 15 pht ch ti. Thm vo bnh 100 ml nc v chun iod gii phng bng dung dch natri thiosulfat 0,1 N (C), ch th l 0,5 ml dung dch h tinh bt (TT) cho vo lc gn cui chun .

1 ml dung dch natri thiosulfat 0,1 N (C) tng ng vi 27,03 mg FeCl3.6H2O.

Dung dch gc mu : Ho tan 60 g cobalt (II) clorid (TT) trong dung mi A cho va 1000 ml. Chun , ri iu chnh bng dung mi A c dung dch cha 59,5 mg CoCl2. 6H2O trong 1 ml.

Chun : Cho vo mt bnh nn dung tch 250 ml c nt mi 5 ml dung dch mu , 5 ml nc oxy gi 10 th tch v 10 ml dung dch natri hydroxyd 30% (TT). un si nh trong 10 pht, ngui ri thm 60 ml dung dch acid sulfuric 1M (TT) v 2 g kali iodid (TT). y bnh v lc nh cho tan tủa, chun iod gii phng bng dung dch natri thiosulfat 0,1 N (TT) vi ch th l 0,5 ml dung dch h tinh bt (TT) cho vo lc gn cui chun . Dung dch chuyn thnh mu hng nht khi chun n im tng ng.

1 ml dung dch natri thiosulfat 0,1N (TT) tng ng vi 23,79 mg CoCl2. 6H2O.

Dung dch gc mu xanh: Ho tan 63 g ng (II) sulfat (TT) trong dung mi A cho va 1000 ml. Chun , ri iu chnh bng dung mi A c dung dch cha 62,4 mg CuSO4. 5H2O trong 1 ml.

Chun : Cho vo mt bnh nn dung tch 250 ml c nt mi 10 ml dung dch mu xanh, 50 ml nc, 12 ml dung dch acid acetic 2 M (TT) v 3 g kali iodid (TT). Chun iod gii phng bng dung dch natri thiosulfat 0,1 N (TT) n khi c mu nu nht, ch th l 0,5 ml dung dch h tinh bt (TT) cho vo lc gn cui chun .

1 ml dung dch natri thiosulfat 0,1 N (TT) tng tng vi 24,97 mg CuSO4. 5H2O.

 

Pha ch cc dung dch mu chun

Dng 3 dung dch gc pha 5 dung dch mu chun theo Bng 9.3.1.

 

 

 

Bng 9.3.1. Cc dung dch mu chun

 

Dung dch mu chun

Dung dch gc

(ml)

Dung dch acid

hydrocloric 1% (kl/tt) (ml)

 

Mu vng

Mu

Mu xanh

N (nu)

30

30

24

16

VN (vng nu)

24

10

4

62

V (vng)

24

6

0

70

VL (vng lc)

96

2

2

0

()

10

20

0

70

 

Pha ch cc dung dch mu i chiu

Dng 5 dung dch mu chun pha cc dung dch mu i chiu theo cc bng 9.3.2a n 9.3.2e sau y:

Bng 9.3. 2a. Dung dch mu i chiu N.

 

Dung dch mu i chiu

Dung dch chun mu N (ml)

Dung dch acid hydrocloric 1% (ml)

N1

75,0

25,0

N2

50,0

50,0

N3

37,5

62,5

N4

25,0

75,0

N5

12,5

87,5

N6

5,0

95,0

N7

2,5

97,5

N8

1,5

98,5

N9

1,0

99,0

 

Bng 9.3.2b. Dung dch mu i chiu VN

Dung dch mu i chiu

Dung dch chun mu VN (ml)

Dung dch acid hydrocloric 1% (ml)

VN1

100,0

0,0

VN2

75,0

25,0

VN3

50,0

50,0

VN4

25,0

75,0

VN5

12,5

87,5

VN6

5,0

95,0

VN7

2,5

97,5

 

 

 

Bng 9.3.2c. Dung dch mu i chiu V

 

Dung dch mu

i chiu

Dung dch chun mu V (ml)

Dung dch acid hydrocloric 1% (ml)

V1

100,0

0,0

V2

75,0

25,0

V3

50,0

50,0

V4

25,0

75,0

V5

12,5

87,5

V6

5,0

95,0

V7

2,5

97,5

 

Bng 9.3.2d. Dung dch mu i chiu VL

 

Dung dch mu i chiu

Dung dch chun mu VL (ml)

Dung dch acid hydrocloric 1% (ml)

VL1

25,0

75,0

VL2

15,0

85,0

VL3

8,5

91,5

VL4

5,0

95,0

VL5

3,0

97,0

VL6

1,5

98,5

VL7

0,75

99,25

 

Bng 9.3.2e. Dung dch mu i chiu

 

Dung dch mu i chiu

Dung dch chun mu (ml)

Dung dch acid hydrocloric 1% (ml)

1

100,0

0,0

2

75,0

25,0

3

50,0

50,0

4

37,5

62,5

5

25,0

75,0

6

12,5

87,5

7

5,0

95,0

 

Bo qun

Vi phng php 1, cc dung dch mu i chiu cn c bo qun trong nhng ng thy tinh trung tnh, khng mu, trong sut c ng knh ngoi 12 mm, c hn kn v trnh nh sng.

Vi phng php 2, cc dung dch mu i chiu phi c chun b ngay trc khi dng t dung dch mu chun.