function calcchr(form,index)
  // converts units for electric charge, Nov. 10, 2004
  // update constants Nov. 11,2007
  // copyright Bernd Krueger, Cactus2000, 2007-2009
{
  var nAvo    = 6.02214179e23;   // Avogadro constant, mol-1 (NIST, CODATA 2006)
  var elChr   = 1.602176487e-19; // e, elementary charge, C (NIST, CODATA 2006)
  var C_statC = 3.335641e-10;    // coulomb per statcoulomb (NIST)

  if(index==-1) { v=form.storev.value; if(v==0) return; }
  if(index==0) v=parseFloat(form.cou.value);            // C (base)
  if(index==1) v=parseFloat(form.amh.value*3600.);      // Ah
  if(index==2) v=parseFloat(form.ele.value*elChr);      // elementary charge
  if(index==3) v=parseFloat(form.abc.value*10.);        // abcoulomb
  if(index==4) v=parseFloat(form.stc.value*C_statC);    // statcoulomb
  if(index==5) v=parseFloat(form.far.value*elChr*nAvo); // faraday           
  form.storev.value=v;

  form.cou.value=ausga(form,v);            // C (base)
  form.amh.value=ausga(form,v/3600.);      // Ah
  form.ele.value=ausga(form,v/elChr);      // elementary charge
  form.abc.value=ausga(form,v/10.);        // abcoulomb
  form.stc.value=ausga(form,v/C_statC);    // statcoulomb
  form.far.value=ausga(form,v/elChr/nAvo); // faraday
  return;
}