The CAS Registry Mumber 68303-34-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,8,3,0 and 3 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 68303-34: (7*6)+(6*8)+(5*3)+(4*0)+(3*3)+(2*3)+(1*4)=124 124 % 10 = 4 So 68303-34-4 is a valid CAS Registry Number.