The CAS Registry Mumber 37311-34-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,7,3,1 and 1 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 37311-34: (7*3)+(6*7)+(5*3)+(4*1)+(3*1)+(2*3)+(1*4)=95 95 % 10 = 5 So 37311-34-5 is a valid CAS Registry Number.