The CAS Registry Mumber 103425-25-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,3,4,2 and 5 respectively; the second part has 2 digits, 2 and 5 respectively. Calculate Digit Verification of CAS Registry Number 103425-25: (8*1)+(7*0)+(6*3)+(5*4)+(4*2)+(3*5)+(2*2)+(1*5)=78 78 % 10 = 8 So 103425-25-8 is a valid CAS Registry Number.