10.1 Phng php chun o Ampe

Trong chun o ampe, im kt thc c xc nh bng cch quan st s bin i ca cng dng in o gia hai in cc (1 in cc ch th v 1 in cc so snh hoc hai in cc ch th) nhng trong dung dch kho st v duy tr mt th hiu khng i. Cng dng in ny l mt hm s m bin s l lng dung dch chun thm vo

Th ca in cc o cn phi m bo dng khuch tn i vi cht in hot.

My

My gm c mt ngun cung cp in th iu chnh c v mt ng h o microampe nhy. H thng pht hin ni chung gm mt in cc ch th (th d: in cc platin, in cc git thu ngn, in cc c a quay hoc in cc than) ghp i vi mt in cc so snh nh in cc calomel hoc in cc bc - bc clorid.

C th dng my c 3 in cc, my ny ngoi in cc ch th v in cc so snh cn c in cc b tr phn cc.

Cch tin hnh

Chnh th ca in cc ch th theo cc ch dn trong chuyn lun ring. Lp th biu din cng dng ban u v cc gi tr cng dng khc thu c trong khi chun , di dng mt hm s vi bin s l lng dung dch chun thm vo. Khi tng lng dung dch chun thm vo t xp x 80% th tch l thuyt dung dch chun cn dng t im tng ng, thm dung dch chun khng t hn 3 ln lin tip tin dn ti im tng ng. Cc gi tr thu c ny cn phi trn mt ng thng. Tip tc thm dung dch chun n qu im tng ng v li thm khng t hn ba ln lin tip dung dch chun na, cc gi tr thu c ln ny phi trn 1 ng thng khc. im kt thc ca php chun l giao im ca hai ng thng ni trn.

Trong trng hp chun o ampe bng hai in cc ch th nn ghi li ton b ng cong chun v dng th ny xc nh im tng ng.

 

 

 

 


Hnh 10.1.S chun o Ampe

 

A: Ngun cung cp dng c th khng i

B: Micro - ampe k

C: in th k

D: Dung dch chun

E: In cc b tr

F: in cc ch th

G: in c so snh

H: Khuy t

 

 

 

 

 

 

 

 

 

 

 

 

 

10.2 Phng php chun o in th

 

Trong chun o in th, im kt thc ca chun c xc nh bng cch quan st s bin i hiu s in th o c gia hai in cc (1 in cc ch th v 1 in cc so snh hoc hai in cc ch th) nhng trong dung dch kho st. S bin i ny nh l mt hm s m bin s l lng dung dch chun thm vo. in th thng c o cng dng in bng khng hoc thc t bng khng.

My

My c s dng (my o th n hoc my c t hp mch in t) gm c mt von k cho php c c ti 1 mV.

Tu theo bn cht ca hp cht cn nh lng m chn in cc ch th, c th l in cc thu tinh hoc in cc kim loi (nh platin, vng, bc, thu ngn....). in cc so snh thng l in cc calomel hoc in cc bc - bc clorid.

Trong chun acid kim, tr trng hp c nhng ch dn khc ca chuyn lun ring, ngi ta thng dng in cc kp thu tinh - calomel hoc thu tinh - bc - bc clorid.

 

Cch tin hnh

Lp th biu din nhng bin i v in th tng ng vi lng dung dch chun thm vo cho n v vt im tng ng gi nh. im kt thc ca chun tng ng vi im m c s thay i t bin v in th.