# Conversion Formulas

### What is Alkalinity?

Alkalinity is defined as a measure of the buffering capacity of water to neutralize strong acid. This capacity is attributed to bases that are present in natural waters including OH-, HCO3-, and CO32-. More alkalinity in your water sample means more buffering capacity of your water sample.

In order to determine Alkalinity of your samples, samples will be titrated with sulfuric acid or hydrochloric acid to a certain pH end point (pH 8.3 for Phenolphthalein Alkalinity and pH 4.5 for Total Alkalinity), and the volume of the acid used for the titration will be recorded.

What is Total Alkalinity?

Total Alkalinity is the amount of acid used to reach pH 4.5. (ml) x 50,000 (mg CaCO3/eq) / sample volume (ml)

Here is an example on how to find Total Alkalinity: 18ml of 0.01M of Sulfuric Acid was required to Titrate 50ml of your sample to pH 4.5.

Total Alkalinity= 18(ml) x 0.02(eq/L) x 50,000 (mg CaCO3/eq) / 50(ml) = 360(mg/L)

### Water Hardness Levels

Soft: 0 to 75 mg/L as CaCO3

Moderate: 76 to 150 mg/L as CaCO3

Hard: 151 to 300mg/L as CaCO3

Very Hard: Above 301 mg/L as CaCO3

Total Hardness = Calcium Hardness + Magnesium Hardness

Water should have a total hardness of less than 75 to 85mg/l as CaCO3 and a magnesium hardness of less than 40mg/l as CaCO3 to minimize scaling at elevated temperatures.

### What’s the formula to convert mg/L to ppm?

1 mg/L = 1 ppm for dilute aqueous solutions. For example, a chlorine concentration of 1.8 mg/L chlorine is equivalent to 1.8 ppm chlorine.

### How can I convert percent transmittance to absorbance, or absorbance to percent transmittance?

To convert a value from percent transmittance (%T) to absorbance, use the following equation:

Absorbance = 2 – log(%T)
Example: convert 56%T to absorbance:
2 – log(56) = 0.252 absorbance units
To convert a value from absorbance to percent transmittance, use the following equation:

%T = antilog (2 – absorbance)
Example: convert an absorbance of 0.505 to %T:
antilog (2 – 0.505) = 31.3 %T
What is a grain per gallon (gpg)?
One grain is equivalent to 64.799 milligrams. It’s a historic unit of weight once used for barleycorn. A grain per gallon is the weight of a substance in one gallon of water, similar to a milligram per liter.

### What’s the formula for converting grains per gallon (gpg) to milligrams per liter (mg/L)?

Multiply gpg by 17.1 to get mg/L (1 gpg = 17.1 mg/L). For example, a hardness test result of 3 gpg as CaCO3 is equivalent to 51 mg/L as CaCO3. What’s the formula for converting grains per gallon to milligrams per liter? 1 grain = 64.799 milligrams 1 gallon = 3.785 liters 64.799 divided by 3.785 liters = 17.1 1 gpg = 17.1 mg/L

### What's the formula for converting calcium carbonate ppm (as CaCO3) to ppm Calcium (ion)?

Multiply ppm (as CaCO3) by 0.4

### Converting calcium carbonate ppm (as CaCO3) to Degrees of General Hardness (dGH)

Simply multiply ppm (as CaCO3) by 0.056

### How do I convert sodium chloride ppm (as NaCl) to chloride (as Cl-1)?

You would multiply ppm (as NaCl) by 0.6097

### What's the formula for converting hexavalent chromium ppm (as Cr+6) to sodium chromate ppm (as Na2CrO4)?

You need to multiply ppm (as Cr+6) by 3.115

### Converting hexavalent chromium ppm (asCr+6) to chromate ppm (as CrO4):

You will multiply ppm (as Cr+6) by 2.231

### How do I convert calcium carbonate ppm (as CaCO3) to magnesium ion (as Mg+2)?

Multiply ppm (as CaCO3) by 0.2439

### What is the formula for converting calcium carbonate ppm (as CaCO3) to magnesium chloride (as MgCl2)?

Multiply ppm (as CaCo3) by 0.956

### What is the formula for converting manganese ppm (as Mn+2) to potassium permanganate (as KMn04)?

Multiply ppm (as Mn+2) by 2.876

### What is the formula for converting manganese ppm (as Mn+2) to potassium permanganate (as MnO4-)?

Multiply ppm (as Mn+2) by 2.165