9.2 XC NH TRONG CA DUNG DCH

trong ca cc dung dch c xc nh bng cch so snh cc dung dch vi cc hn dch i chiu.

Dung dch Hydrazin sulfat: Ho tan 1,0 g hydrazin sulfat (TT) trong nc, pha long thnh 100,0 ml v yn trong thi gian 4 n 6 gi.

Dung dch Hexamethylentetramin: Trong mt bnh nn nt thy tinh mi dung tch 100 ml, ha tan 2,5 g hexamethylentetramin trong 25,0 ml nc.

Hn dch c gc:

Thm 25,0 ml dung dch hydrazin sulfat (TT) vo 25,0 ml dung dch hexamethylentetramin, lc k v yn trong 24 gi.

Nu c bo qun trong l thu tinh tt (khng c khuyt tt b mt) th hn dch c gc bn vng trong vng 2 thng. Hn dch ny phi khng c bm dnh vo thu tinh v phi c lc k trc khi dng.

Chun c: Pha long 15,0 ml hn dch c gc thnh 1000,0 ml vi nc.

Chun c c chun b ngay trc khi dng v c th bo qun ti a trong vng 24 gi.

Hn dch i chiu

Cc hn dch i chiu t I ti IV c chun b nh ch dn trong Bng 9.2.

Mi hn dch phi c trn k v lc trc khi s dng.

Bng 9.2

 

I

II

III

IV

Chun c (ml)

 

5,0

10,0

30,0

50,0

Nc

95,0

90,0

70,0

50,0

Cch th

Vic so snh c tin hnh trong cc ng nghim ging nhau, bng thu tinh trung tnh, trong, khng mu, y bng, c ng knh trong khong t 15 n 25 mm. Chiu dy ca lp dung dch th v ca hn dch chun i chiu l 40 mm. Hn dch chun i chiu sau khi pha 5 pht phi c so snh ngay vi dung dch cn th bng cch quan st cht lng t trn xung trong cc ng nghim trn nn en di nh sng khuch tn ban ngy. nh sng khuch tn phi ph hp c th phn bit c hn dch i chiu I vi nc ct v vi hn dch i chiu II.

Cch nh gi kt qu

Mt cht lng c coi nh trong nu n tng ng vi trong ca nc hay ca dung mi dng khi th nghim trong nhng iu kin nh m t, hoc nu cht lng hi c nh th cng khng c c qu hn dch chun i chiu s I.

Cc yu cu khc nhau v c c biu th theo hn dch chun i chiu s I, II, III, v IV.