function vulin()
{
document.ryznar.ph.value=7.7
document.ryznar.tds.value=20
document.ryznar.Ca.value=5
document.ryznar.HCO3.value=10
document.ryznar.temperatuur.value=20
bereken()
}

function vulinsea()
{
document.ryznar.ph.value=8	
document.ryznar.tds.value=34483
document.ryznar.Ca.value=400
document.ryznar.HCO3.value=140
document.ryznar.temperatuur.value=20
bereken()
}

function vulintap()
{
document.ryznar.ph.value=8.6	
document.ryznar.tds.value=273
document.ryznar.Ca.value=49
document.ryznar.HCO3.value=121
document.ryznar.temperatuur.value=20
bereken()
}

function bereken()
{
var ph=document.ryznar.ph.value
var tds=document.ryznar.tds.value
var Ca=document.ryznar.Ca.value
var HCO3=document.ryznar.HCO3.value
var phs,Ka2,Ksp,gammaCa,gammaHCO3,I
var temperatuur=document.ryznar.temperatuur.value

var eenheidCa=document.ryznar.eenheidCa.value
var eenheidHCO3=document.ryznar.eenheidHCO3.value
var eenheidEC=document.ryznar.eenheidEC.value
var eenheidtemp=document.ryznar.eenheidtemp.value

if 		(eenheidCa=="1"){Ca=Ca/(40e3)}
else if (eenheidCa=="2"){Ca=Ca/(40e3)}
else if (eenheidCa=="3"){Ca=Ca/(40e3)}
else if (eenheidCa=="4"){Ca=Ca}
else if (eenheidCa=="5"){Ca=Ca*1e-3}
else if (eenheidCa=="6"){Ca=Ca/2}
else if (eenheidCa=="7"){Ca=Ca*1e-3}

if 		(eenheidHCO3=="1"){HCO3=HCO3/(61.02e3)}
else if (eenheidHCO3=="2"){HCO3=HCO3/(61.02e3)}
else if (eenheidHCO3=="3"){HCO3=HCO3/(61.02e3)}
else if (eenheidHCO3=="4"){HCO3=HCO3}
else if (eenheidHCO3=="5"){HCO3=HCO3*1e-3}
else if (eenheidHCO3=="6"){HCO3=HCO3/1}
else if (eenheidHCO3=="7"){HCO3=HCO3/1*1e-3}

/*
if 		(eenheidEC=="1"){tds=tds}
else if (eenheidEC=="2"){tds=tds*1e-3}
else if (eenheidEC=="3"){tds=tds*1e-6}
else if (eenheidEC=="4"){tds=tds*1e-3}
else if (eenheidEC=="5"){tds=tds*1e-4}
else if (eenheidEC=="6"){tds=tds*1}
else if (eenheidEC=="7"){tds=tds*100}
else if (eenheidEC=="8"){tds=tds*1.563e-6}
else if (eenheidEC=="9"){tds=tds*1.563e-6}
*/
if 		(eenheidEC=="1"){tds=tds}
else if (eenheidEC=="2"){tds=tds}
else if (eenheidEC=="3"){tds=tds*2.3904*1e6}
else if (eenheidEC=="4"){tds=tds*2.3904*1e3}
else if (eenheidEC=="5"){tds=tds*2.3904}
else if (eenheidEC=="6"){tds=1/tds*2.3904*1e6}
else if (eenheidEC=="7"){tds=1/tds*2.3904*1e8}

if 		(eenheidtemp=="1"){temperature=temperatuur}
else if (eenheidtemp=="2"){temperature=0.555*(temperatuur-32)}
else if (eenheidtemp=="3"){temperature=temperatuur-273}

if(ph&&tds&&Ca&&HCO3&&temperature)
{
I=2.5e-5*tds

with(Math)
{
Ka2=0.0928e-11*temperature+2.2927e-11
Ksp=9.235e-9*Math.exp(-0.0273*temperature)
a=Math.sqrt(I)
b1=(-0.5*4*a/(1+a))
b2=(-0.5*a/(1+a))
gammaCa=Math.pow(10,b1)
gammaHCO3=Math.pow(10,b2)
phs=-log((Ka2*gammaCa*Ca*gammaHCO3*HCO3)/Ksp)/log(10)
}

ri=2*phs-ph

if 		(ri<=5.5)				{riindex="Heavy scale will form"}
else if	(ri>5.5 && ri<=6.2)		{riindex="Scale will form"}
else if	(ri>6.2 && ri<=6.8)		{riindex="No difficulties"}
else if	(ri>6.8 && ri<=8.5)		{riindex="Water is aggressive"}
else if	(ri>8.5)				{riindex="Water is very aggressive"}

if		(ri>=4 && ri<=5)		{riindexcarrier="Heavy scale"}
else if	(ri>5  && ri<=6)		{riindexcarrier="Light scale"}
else if (ri>6  && ri<=7)		{riindexcarrier="Little scale or corrosion"}
else if (ri>7  && ri<=7.5)		{riindexcarrier="Corrosion significant"}
else if (ri>7.5 && ri <=9.0)	{riindexcarrier="Heavy corrosion"}
else 							{riindexcarrier="Corrosion intolerable"}

document.ryznar.phs.value=phs.toPrecision(2)
document.ryznar.phs.className="blauw"

document.ryznar.ri.value=ri.toPrecision(2)
document.ryznar.ri.className="blauw"

document.ryznar.riindex.value=riindex
document.ryznar.riindex.className="blauw"
	
document.ryznar.riindexcarrier.value=riindexcarrier
document.ryznar.riindexcarrier.className="blauw"
	
}
else{alert("You have to fill all the boxes with *")}
}