The CAS Registry Mumber 351-68-8 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 3,5 and 1 respectively; the second part has 2 digits, 6 and 8 respectively. Calculate Digit Verification of CAS Registry Number 351-68: (5*3)+(4*5)+(3*1)+(2*6)+(1*8)=58 58 % 10 = 8 So 351-68-8 is a valid CAS Registry Number.