the following must apply due to the mass maintenance in the stationary state it thus results for the mass balance or instant electrolyte balance at the patient side in the dialysis expressed by values at the dialysate side u03b4 j b q d c di u2212 q d q f c do q d c di u2212 c do u2212 q f c do equation 3 u03b4j gt 0 means that an electrolyte is transferred into the patient u03b4j lt 0 that it is removed from him it is assumed in simplified terms for the splitting off of the diffuse portion that the convective transport through the ultrafiltration does not influence the output concentration at the dialyzer 60 this assumption is satisfied very well for small molecules and ions in general u03b4 j diff q d c di u2212 c do equation 4 it must be taken into account in the calculation of the electrolyte balance that a delay time t f passes between the inlet of fresh dialysate with the concentration c do this depends on the machine hydraulics the dialyzer volume and the dialysate flow the electrolyte quantity transferred between the dialysate and the patient is obtained by integration while taking account of the delay time accumulative balance while taking account of the delay time if the distribution volume v of the patient is known it can be estimated at any time in the 1 pool model by which amount dc pat the mean electrolyte concentration in the patient has changed this change.