Inhibitor

Conc. ppm

Hydrogen evolved ml

θ

%IE

Catharanthus extract

1 M HCl

6.20

---

---

50

4.60

0.258

25.8

100

3.60

0.419

41.9

150

3.20

0.484

48.4

200

2.70

0.565

56.5

250

2.40

0.613

61.3

300

2.20

0.645

64.5