The CAS Registry Mumber 76308-31-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,6,3,0 and 8 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 76308-31: (7*7)+(6*6)+(5*3)+(4*0)+(3*8)+(2*3)+(1*1)=131 131 % 10 = 1 So 76308-31-1 is a valid CAS Registry Number.