Milero's synthetic seawater recipe question

[AcroporAddict]

Here is the Frank Millero Synthetic Seawater Recipe from one of Randy's Articles. I just want to clarify something for my own understanding.

An Artificial Seawater Recipe
For those who are interested, the following artificial seawater recipe is taken from "Chemical Oceanography" by Frank Millero. It makes a recipe that matches 35 ppt seawater in terms of major ions, but does not try to match all minor and trace elements, most of which will be present as impurities in the major elements.

23.98 g sodium chloride
5.029 g magnesium chloride
4.01 g sodium sulfate
1.14 g calcium chloride
0.699 g potassium chloride
0.172 g sodium bicarbonate
0.100 g potassium bromide
0.0254 g boric acid
0.0143 g strontium chloride
0.0029 g sodium fluoride
Water to 1 kg total weight.

The water to 1 kg total weight means that since the total dry ingredients weigh 35.1726 grams, then the amount of water weighs 1000 grams - 35.1726 grams, or 964.82 grams of water, correct?

I am going to make my own salt and just wanted to make sure I was correct on the last part so I can multiply the weights to get the amounts of each ingredient to make 25 gallon batches of salt mix.

 

[loudell]

How are you going to be sure that your powder ingredients do not contain and moisture that will contribute to weight? Especially when some of the measurements are precise to a ten-thousandth of a gram??
I am just curious.....

 

[AcroporAddict]

I'm not. I'm going to try this based on the recipe and just see how it goes.

Can you answer my original question in post 1? I just want to make sure I am reading the last part right.

 

[Maivortex]

You are correct but weighing the water is not the practical way. Add the ingredients to about 75% of your total volume, dissolve everything than top off to one liter (if you were making one liter/ since one liter weighs 1000g)

 

[AcroporAddict]

You are correct but weighing the water is not the practical way. Add the ingredients to about 75% of your total volume, dissolve everything than top off to one liter (if you were making one liter/ since one liter weighs 1000g)

Not doing it that way. I realize the minor elements are quite small in weight. What I am doing is mixing up the chemicals in weight amounts that will make 25 gallons of saltwater, or specifically the amount of chemical needed to add to 25 gallons of RODI.

In other words, the Milero recipe calls for 35.1726 grams of chemical and 964.82 grams of water for 1 kg total weight. Divide the gram weight of 25 gallons of water by 964.92 and you get 98 (rounded). Multiply each dry ingredient weight by that multiplier and you get the total weight of each chemical needed to add to 25 gallons of water to make that volume of 35 ppt synthetic seawater.

Doing it in 25 gallon batches makes the minor chemicals easier to weigh and work with.

 

[teesquare]

I am just curious...WHY bother to make your own salt? Is it that you feel you can save money, or get a better quality salt? Or just for fun?
T

 

[Boomer]

Acro and Mai

Add the ingredients to about 75% of your total volume, dissolve everything than top off to one liter (if you were making one liter/ since one liter weighs 1000g)

You can not do that either, as you do not know the salt dry weigh water displacement. Pretend the salt dry weight water displacement is 20 ml of water. Then, 1,000 - 20 = 980 ml or grams of water added your way. That is 15.18 g or ml of to much water, i.e, 980 - 964.82. That gives about ~ 2 % lower than 35 ppt or ~ 34. ppt. 35.1726 g of salt is not going to equal or displace water to 35.1726 ml.


It is best to do this

35.1726 grams, or 964.82 ml of water, as 1 ml = 1 gram

Add 500ml of water, add salt and stir well, then add the rest of the water vol or 464.82 ml

As Lou is trying to point out all the ingredients have to be all anhydrous. You can not use something like CaCl2 · 2H20 i.e., Calcium Chloride dihydrate or hexahydrate, etc. for that mixture. Most is sold as CaCl 2 · 2H2O and you have to correct for that water. Meaning, you will be adding less ml of water as the ml of water need for the total of 964 will be in part the water added from the CaCl 2 · 2H2O and other salt that have water in them. For example, this 1.14 g calcium chloride will be more than 1.14 g. So, to stay with that 1.14 g, it is has to be pure Calcium Chloride Anhydrous. In Millero's book he goes into great detail on how to account for the water. For you, you are going to need a data sheet showing the % water content. Now, if use all anhydrous, as shown by Millero, the water % will be of little off-set and close enough for a tank but not a NSW std. But most of these, if you go look, will not be found as anhydrous. So, you will HAVE to adjust for water content in the salt used for the mix. There is a huge difference in Calcium Chloride anhydrous vs dihydrate vs hexahydrate

Calcium Chloride anhydrous = 110.98 g/mol (anhydrous)

Calcium Chloride dihydrate = 147.014 g/mol (dihydrate)

Calcium Chloride hexahydrate = 219.08 g/mol (hexahydrate)

As you can see the hexa is 50 % water. If you look at that 1.14 g calcium chloride and use hexa the weight will need to be almost doubled to ~ 2.25 grams to get the same amount of Calcium and Chloride equal to the Calcium and Chloride found in 1.14 g calcium chloride.

 

[AcroporAddict]

I am just curious...WHY bother to make your own salt? Is it that you feel you can save money, or get a better quality salt? Or just for fun?
T

Just for fun, really. But, with the ingredients I have, after the initial investment, which is not a lot, you get to about $10 for 200 gallons. the minor use chemicals won't have to be replaced too often, but things like Nacl are inexpensive, and I think the calcium chloride will be the most expensive single ingredient.

A Boomer said, I may need to adjust the amounts of certain chemicals. I was going to mix a 25 gallon batch up the way I outlined, then do a calcium/alkalinity/magnesium test and see what the levels are. I assumed there would be a little tweaking along the way.

 

[teesquare]

Sounds interesting! Please keep us informed. I read my earlier post - I do not want to take it as a dis-couragement, rather - I am just interested in all "outside the box" thinking.

I am looking forward to your experiments!

T

 

[Boomer]

Note:

The salts used in this hobby, IO, RC, TMP etc, have from 2 - 6 % water. So, that means, if you mixed up 35 grams of salt x and added it ot 965 ml of water, the end salinity will be from 31 -34 ppt and not 35 ppt.

This can can be clearly seen here

The Composition Of Several Synthetic Seawater Mixes
http://www.reef-guardian.com/files/sels.pdf



35 ppt NSW or 35 g /kg, against other salt mixes weighted to 35 grams in 965 ml of water or 35 g /kg.

29.65, 32.64, 29.40, 28.91, 30.07, 28.85, 28.39, 29.54 ppt

Look at this one 28.85, 35 - 28.85 = 6.42 % water = 6.42 ppt water in that 35 grams = 28.85 ppt seawater

 

[AcroporAddict]

Sounds interesting! Please keep us informed. I read my earlier post - I do not want to take it as a dis-couragement, rather - I am just interested in all "outside the box" thinking.

I am looking forward to your experiments!

T

I appreciate it, and all other advice and comments.

One reason I am interested in trying it is that I have only seen two other threads on Reef Central even talking about a DIY synthetic seawater mix, and nothing elsewhere. I don't know if this is because no one has thought of trying it, or if folks think it simply costs too much to do it, or you need a Randy Holmes Farley level of chemistry knowledge to do it. As always, thank you Randy for all your articles on reef chemistry, they are the foundation for any reef chemistry knowledge I do have.

I have CaCl hexahydrate right now, so I will expect after this first batch my calcium level will be about half what it should be, so I may need to switch to anhydrous.

 

[bertoni]

There are some threads on it. I think most people don't do this because getting suitably pure chemicals is rather expensive, so the cost savings tends to be small.

You probably could dry the calcium chloride in an oven, although it'll form a brick, I think. Other chemicals might work, as well.

 

[AcroporAddict]

There are some threads on it. I think most people don't do this because getting suitably pure chemicals is rather expensive, so the cost savings tends to be small.

You probably could dry the calcium chloride in an oven, although it'll form a brick, I think. Other chemicals might work, as well.

Jonathan,
Do you have any idea as to the purity level of what goes into a salt mix like instant ocean. I have seen lots of brown frothy stuff in plenty of salt mixes I have used, so I figured they deifintely were not reagent grade, and maybe not lab grade, but probably food grade.

My NaCl and KCl are water softening Products. They are pure without any additives and anti-caking agents. Made to go into home water softening sytems. Fit for human consumption. A 40# bag of Morton NaCl crystals is about $6 and a 40# bag of KCl crystals is about $21.

 

[bertoni]

I don't know the purity levels used, but the NaCl would only be one component. The less common items, like the magnesium, strontium, etc, might be more problematic.

 

[AcroporAddict]

I'll make up my first 25 gallon batch of salt mix and make 25 gallons of water tomorrow and post the test results I get: SG, Ca, Mag, KH. This should be a starting point of tweaking the mix with extra calcium or whatever to get NSW levels of SG, Calcium and Magnesium. I have a 60 gallon reef with some fish, anemones, zoas and a couple soft and LPS corals. Probably do some daily 5 gallon water changes and just observe.

Hopefully, I won't be observing my animals in a state of stress!!!

I'll also keep a large volume of commercial salt prepared water on hand in case I have to do an emergency water change!

 

[noobtothereef]

why is everybody talking about water in the dry components? who cares.... mix the dry components thoroughly and mix till you have 1.026/35ppt and call it a day.......

 

[keokea]

Did you ever go through with this?