The CAS Registry Mumber 68330-42-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,8,3,3 and 0 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 68330-42: (7*6)+(6*8)+(5*3)+(4*3)+(3*0)+(2*4)+(1*2)=127 127 % 10 = 7 So 68330-42-7 is a valid CAS Registry Number.