var R = 8.314472 //ideal gas constant
var atmPressure = 101.325 //atmospheric pressure in kPa
var S = 87 //general entropy of vaporization at atmospheric pressure
var pressureMargin = 1.5;

//set the default values
var pressureUnits = "psi"
var solvent = "general"

function calculateBoilingPressure(){ //calculate the minimum pressure required to keep the solvent liquid

var temperature = Number(document.boilingPoint.temperature.value) + 273.15; //get the entered temperature as a number and convert to Kelvin

var kwnBoilingTemp = Number(document.boilingPoint.boilingTemperature.value) + 273.15; //get the known boiling point temperature as a number and convert to Kelvin

pressureInAtm = Math.exp((-S/R*((1.8*((kwnBoilingTemp/temperature)-1))-(0.8*(Math.log(kwnBoilingTemp/temperature)))))); //calculate pressure in atm
pressure = (pressureInAtm*atmPressure) //convert pressure in atm to kPa

pressureUnits = getSelectedValue("pressureUnits"); //get the selected unit of pressure


//convert the result to the selected unit of pressure
if (pressureUnits=="psi") {
	pressure = pressure*0.14503773773020923;
}
else if (pressureUnits=="bar") {
	pressure = pressure/100;
}
else {
alert("Pressure unit error! Please contact the webmaster");
}

document.boilingPoint.answer.value = pressure.toFixed(1)+" "+pressureUnits; //display the answer

if ((pressureInAtm*pressureMargin) < 2.76){
document.getElementById("BPRPressure").innerHTML = "Suggested** BPR 40 psi &#40;Tan&#47;Blue&#41;";
document.boilingPoint.bprImage.src = "pressure_files/P-761.jpg";
}
else if (((pressureInAtm*pressureMargin) > 2.76) && ((pressureInAtm*pressureMargin) < 5.1)){
document.getElementById("BPRPressure").innerHTML = "Suggested** BPR 75 psi &#40;Tan&#47;Yellow&#41;";
document.boilingPoint.bprImage.src = "pressure_files/P-762.jpg";
}
else if (((pressureInAtm*pressureMargin) > 5.1) && ((pressureInAtm*pressureMargin) < 6.8)){
document.getElementById("BPRPressure").innerHTML = "Suggested** BPR 100 psi &#40;Tan&#47;red&#41;";
document.boilingPoint.bprImage.src = "pressure_files/P-763.jpg";
}
else if (((pressureInAtm*pressureMargin) > 6.8) && ((pressureInAtm*pressureMargin) < 17)){
document.getElementById("BPRPressure").innerHTML = "Suggested** BPR 250 psi &#40;Tan&#47;white&#41;";
document.boilingPoint.bprImage.src = "pressure_files/P-764.jpg";
}
else if (((pressureInAtm*pressureMargin) > 17) && ((pressureInAtm*pressureMargin) < 34)){
document.getElementById("BPRPressure").innerHTML = "Suggested** BPR 500 psi &#40;Tan&#47;green&#41;";
document.boilingPoint.bprImage.src = "pressure_files/P-765.jpg";
}
else if (((pressureInAtm*pressureMargin) > 34) && ((pressureInAtm*pressureMargin) < 68.9)){
document.getElementById("BPRPressure").innerHTML = "Suggested** BPR 750 psi &#40;black&#47;blue&#41;";
document.boilingPoint.bprImage.src = "pressure_files/P-765.jpg";
}
else {
document.getElementById("BPRPressure").innerHTML = "Suggested** BPR 1000 psi &#40;Tblack&#47;green&#41;";
document.boilingPoint.bprImage.src = "pressure_files/P-796.jpg";
}
}

function getSelectedValue(radioButtonsName) {
//this function goes through all of the radio button options and finds and returns the one that has been selected. Note you must supply the radio buttons 'name'

chosenValue = ""
len = document.getElementsByName(radioButtonsName).length;
for (i = 0; i <len; i++) {
	if (document.getElementsByName(radioButtonsName)[i].checked) {
		chosenValue = document.getElementsByName(radioButtonsName)[i].value
	}
}
return chosenValue;
}

function setEntropyValue() {  //set the data based on the chosen solvent, if other as for an entropy value. If general give the boiling temperature option.
solvent = document.boilingPoint.entropyValueList.options[document.boilingPoint.entropyValueList.selectedIndex].value;

if (solvent == "1Butanol"){
	S = 87;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 117.6;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "1Propanol"){
	S = 86.6;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 97;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "aceticAcid"){
	S = 87;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 118;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "acetone"){
	S = 85.6;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 56.2;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
				document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "acetonitrile"){
	S = 86.2;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 81.6;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
				document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "benzene"){
	S = 86.2;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 80.1;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "carbonTetrachloride"){
	S = 86.1;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 76.7;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "chloroform"){
	S = 85.7;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 61.2;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "cyclohexane"){
	S = 73.9;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 86.2;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "Dichloromethane"){
	S = 85.2;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 39.8;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "diethyleneGlycol"){
	S = 89.4;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 245;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "diglyme"){
	S = 87.9;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 162;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "DME"){
	S = 86.3;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 85;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "DMF"){
	S = 87.8;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 153;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "dimethylSulfoxide"){
	S = 88.4;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 189;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "dioxane"){
	S = 86.7;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 101.1;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "ethanol"){
	S = 86.2;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 78.5;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "ether"){
	S = 85;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 34.6;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "ethyl Acetate"){
	S = 86.1;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 77;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "ethylene Glycol"){
	S = 88.6;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 197;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "heptane"){
	S = 86.6;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 98;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "hexane"){
	S = 85.9;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 69;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "isopropanol"){
	S = 86.3;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 82.4;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "methanol"){
	S = 85.8;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 64.6;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "methylEthylKetone"){
	S = 86.2;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 79.6;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "MTBE"){
	S = 85.6;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 55.2;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "pXylene"){
	S = 87.5;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 183.3;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "pentane"){
	S = 85.1;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 36.1;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "tButylAlcohol"){
	S = 86.2;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 82.2;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "THF"){
	S = 85.6;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 66;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "toluene"){
	S = 86.9;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S+"*";
	document.boilingPoint.boilingTemperature.value = 110.6;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	}
}
else if (solvent == "water"){
	S = 109;
	document.boilingPoint.entropyValue.disabled=true;
	document.boilingPoint.entropyValue.value=S;
	document.boilingPoint.boilingTemperature.value = 100;
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=false;
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
	else{
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
				document.getElementById("BPRPressure").innerHTML = "";
	}
}
else {
		S = 87;
		document.boilingPoint.entropyValue.disabled=false;
		document.boilingPoint.entropyValue.value = S;
		document.boilingPoint.boilingTemperature.disabled=false;
		document.boilingPoint.boilingTemperature.value="?";
		document.boilingPoint.temperature.disabled=true;
		document.boilingPoint.answer.value="";
		document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
		document.getElementById("BPRPressure").innerHTML = "";
	
}
}

function checkEntropyValue() { //check to see if we have a valid entropy value
if (checkForANumber(document.boilingPoint.entropyValue.value) == "true"){
	S = Number(document.boilingPoint.entropyValue.value);
	document.boilingPoint.boilingTemperature.disabled=false;
	
	//if we have all the other information as well calculate the pressure
	if ((checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
		calculateBoilingPressure();
	}
}
else {
	document.boilingPoint.boilingTemperature.disabled=true;
	document.boilingPoint.temperature.disabled=true;
	document.boilingPoint.answer.value="";
	document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
	document.getElementById("BPRPressure").innerHTML = "";
}
}

function checkBoilingTemperatureValue() { //check to see if we have a valid value in the boiling temperature
if (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true"){
	document.boilingPoint.temperature.disabled=false;
	
	//if we have a valid value and all of the other boxes are valid then calculate the pressure
	if ((checkForANumber(document.boilingPoint.entropyValue.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
	calculateBoilingPressure();
	}
}
else{  //not a valid value so disable the other boxes and clear any old answers
	document.boilingPoint.temperature.disabled=true;
	document.boilingPoint.answer.value="";
	document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
	document.getElementById("BPRPressure").innerHTML = "";
}
}

function checkTemperatureValue() { //check to see if we have a valid value in the temperature, if we do calculate the pressure
if (checkForANumber(document.boilingPoint.temperature.value) == "true"){
	calculateBoilingPressure();
}
else { //not a valid value so clear any old answers
document.boilingPoint.answer.value="";
document.boilingPoint.bprImage.src = "pressure_files/blank.gif";
document.getElementById("BPRPressure").innerHTML = "";
}
}

function clearPromptValue(textboxName) { //clears the '?' when a users clicks in the box
if (document.getElementById(textboxName).value == "?"){
document.getElementById(textboxName).value ="";
}
}

function checkForANumber(value) { //checks to see if the value entered is a number
if ((document.boilingPoint.entropyValue.value.indexOf("*") > -1) && (document.boilingPoint.entropyValue.disabled = true)){ //checks to see if a * is on the end of the value, if it is and the box is disabled (ie we put it there) then remove it
value = value.substring(0, value.length-1)
}
if(isNaN(value)){ //checks to see if it is a number

	return "false";
}
else if (value == ""){ //checks to see if it is empty as checking for a number stangely returns true if empty
	return "false";
}
else if (value.indexOf(" ") > -1) { //checks to see if it is contains a space as checking for a number stangely returns true if using only spaces
		return "false"
}
else{
	return "true";
}
}

function pressureUnitChange(){ //if the pressure units are changed and we have all the information needed for the calculation then run it

if ((checkForANumber(document.boilingPoint.entropyValue.value.substring(0, document.boilingPoint.entropyValue.value.length-1)) == "true") && (checkForANumber(document.boilingPoint.boilingTemperature.value) == "true") && (checkForANumber(document.boilingPoint.temperature.value) == "true")){
	calculateBoilingPressure();
}
}