At present, most of the clinical chemistry laboratory and analytical chemistry of the pharmacy worldwide use the equation of dilution in the preparation of calibration STD curve constructed from several number of points run in arithmetic progression manner. The equation of dilution "v1=m2.v2 /m1 " has problems concerning shortage of stock STD and increasing error possibilities because from its own idea of explanation depends on dilution one step "number of moles before and after the step of dilution is constant", so I introduce an alternative method (Arithmetic progression way in the calibration STD curve) which from its own idea depends on the available volume (Av), {Av =¿stdv IAP= n÷2(n-1)d}, the equation which solve the problems of equation of dilution, furthermore can be used to modify sensitive device automatic pipette to suck solution in arithmetic progression manner depending on difference and available volume, (A.P.W automatic pipette). Key words: calibration STD curves -equation of dilution- equation of prime arithmetic-dilution equation - APW automatic pipette.