**Simplified Metric Method for calculating the amount of masterbatch lye to make for any given container (metric only):**
Container Volume => Fill the container to the desired fill point (not the top), then measure the volume in millilitres.

Sodium Hydroxide (dry, in grams) = Container Volume x 0.75

Water (in grams) = Container Volume x 0.75

If a person has a jug of unknown volume to use as a lye container, here's how to calculate the weight of water and NaOH needed to make just the right amount of 50% NaOH solution for the jug ---

Put the jug on your scale and tare the scale.

Fill the jug with water to the level you want. (Hopefully you won't fill it to the brim for safety's sake.) Weigh the amount of water in the jug.

Times that weight by 1.5 to estimate the weight of 50% masterbatch NaOH solution needed.

Divide that answer by 2 to get the weight of water and of dry NaOH to measure.

Weight of masterbatch solution = Weight of water in the jug X 1.5

Weight of dry NaOH to make this solution = Weight of masterbatch solution / 2

Weight of water = Weight of dry NaOH

Note: DeeAnna's weight measurement method is technically correct, and is the technique to use where accuracy is important.

@Kim2au If you have measured the volume you get from the two equal parts, as

described in my earlier post above, then that measurement can be converted to density (for your time and place) by dividing the volume in millilitres into your original weight in grams (eg. 200grams/131.1millilitres = density). This method is technically correct (larger volumes for testing give more accurate figures), but thank you to DeeAnna for providing the rough density (1.5), which is all we require in this instance

Because you are using the metric system and you only need to measure with a modest amount of accuracy (you are aiming to partially fill a jug), DeeAnna's instructions can be significantly simplified.

Reason:

Water has roughly the same weight as volume (1 litre = 1 kilogram, 1 millilitre = 1 gram).

Background:

The gram was originally defined as the mass of 1 mL of water (at a set temperature and pressure, see

link)

Trivia: The word

*litre* is derived from an older French unit, the

*litron*, whose name came from Greek - where it was a unit of weight, not volume (see

link)

Method:

Fill the container then measure the volume of water.

Use millilitres and grams to measure with the appropriate level of accuracy (litres and kilograms would be too large)

The volume in ml is the weight in grams

Simplification:

This simplifies DeeAnna's instructions (where the lye solution has a density of 1.5) to read that each of the water and lye (by weight) will be 0.75 times the volume of the container.

Example:

Eg. If you have a 2 litre container, and choose to fill it 1,800ml:

Sodium Hydroxide = 1,800 grams x 0.75 of sodium hydroxide = 1,350 grams

Water = 1,800 grams x 0.75 = 1,350 grams

(Check: Masterbatch total = 1,800 grams x 1.5 = 2700 grams, and 1,350 grams + 1,350 grams = 2,700 grams)

**Simplified Metric Method for calculating the amount of masterbatch lye to make for any given container (metric only):**
Container Volume => Fill the container to the desired fill point (not the top), then measure the volume in millilitres.

Sodium Hydroxide (dry, in grams) = Container Volume x 0.75

Water (in grams) = Container Volume x 0.75