Measured Density of Dry Chemicals

(I also have this post duplicated at this post on the TroubleFreePool forum.)

I just used some Borax for the first time to raise pH. Usually, I've never had to adjust pH or sometimes had to add a small amount of acid, but since I've been using Trichlor pucks to raise the CYA level, I've had to raise the pH. In the past, I used Sodium Carbonate, but this time used Borax.

Anyway, the point of this thread is to gather real-world measurements of the density of dry chemical products. This is because the "standard" density of solid sodium tetraborate decahydrate is 1.71 g/ml but my measured density using a measuring cup and scale is 0.96 g/ml (about 1 ounce weight per fluid ounce). I had a similar experience with sodium bicarbonate solid as 2.159 while my own measurement was 1.2 g/ml. Calcium Chloride Anhydrous is 2.16 g/ml as a solid but I measured 1.2 g/ml for granules (tiny round pellets). The differences are due to the density of a solid block of substance vs. the powdered versions that we buy and that are far easier to dissolve.

So I would like other's to post their measurements. They can be in ounces weight per fluid ounce or ounces weight per cup or whatever you want. Try to tap your measuring cup on a hard surface to make the contents settle. That will result in more consistent numbers. The following is a list of dry chemicals where such density measurements would be useful. This would allow us to specify volume instead of weight for those that find it more convenient.

The theoretical "solid" density follows each item. By the way, 1 fluid ounce volume per ounce weight is equal to 0.9586 g/ml

Code:

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                                                    DENSITY (g/ml)
Pool Chemical                                        Solid    Bulk
Sodium Bisulfate (Dry Acid) ........................ 2.435    1.44
Sodium Carbonate (Soda Ash / Washing Soda / pH Up) . 2.532    1.1
Sodium Tetraborate Decahydrate (20 Mule Team Borax)  1.71    1.0 (tapped) / 0.757 (scooped)
Sodium Tetraborate Pentahydrate (Proteam Supreme?) . 1.81      ?
Sodium Bicarbonate (Baking Soda) ................... 2.159    1.2
Calcium Hypochlorite (Cal-Hypo) .................... 2.35    1.025 (MSDS)
Dichlor Dihydrate Granules/Powder ..................  ?      0.985
Dichlor Anhydrous Granules/Powder ..................  ?      0.7 (Wikipedia)
Lithium Hypochlorite Granules/Powder ...............  ?      0.98
Potassium Monopersulfate (Non-Chlorine Shock) ......  ?      1.15-1.30 (MSDS)
Calcium Chloride Dihydrate .........................  ?      0.837
Calcium Chloride Anhydrous ......................... 2.16    1.2
Cyanuric Acid ...................................... 2.5      0.765 (0.92 from unknown source)
Salt ............................................... 2.16    1.154

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Thanks,
Richard

Somwhat off topic, but I noticed from your post you are using trichlor pucks to raise your cya.

Have you an algorithm for calculating the number of pucks needed to increase cya per unit of volume?
I am trying to do the same thing and am wondering whether adding cya directly may be easier.
thx

The CYA pucks vary in size and the ones I am using are 3" and 8 ounces weight. There are also 7 ounce and 6 ounce versions that are also 3" in diamter. There are 3 ounce 1" and 1 onuce 1/2" pucks (or tablets) as well.

Anyway, one 3" 8 ounce puck will add 5.5 ppm FC and 3.3 ppm CYA in 10,000 gallons. An even faster way to add CYA and chlorine at the same time that dissolves faster and has more CYA in it is to use Dichlor powder where 1 pound (16 ounces) will add 6.6 ppm FC and 6.0 ppm CYA in 10,000 gallons. To add CYA by itself quickly, there is the Natural Chemistry product called Instant Pool Water Conditioner found at this link. And of course you can add regular CYA though that is very slow to dissolve (putting it in sock/hose over a return makes it dissolve faster).

Richard

I have a 5lbs container of CYA from Home Depot. I measured the volume to be about 10.5 cups so the density is close to 2270/2478 = .92 g/ml which is pretty far off of theoretical. The granuals are fairly large which might account for the difference.

Thanks Richard this is most helpful.

Since I started at a cya of 0 this year and have a 30K+ pool I will need a lot of pucks to get to 40-50. Your analysis also explains the modest increase in cya I have seen to date after 20 pucks.

One advantage of bringing up the cya slowly with pucks, is that the FC that I can maintained consistently is 4.5-8 (depending on the number of pucks used simultaneously) and this is a very effective algaecide at the low cyas seen early after opening. My pool is always green and murky on opening no matter how good the cover is (the joys of being surrounded by large trees), but is crystal clear at the end of 7 days after lots of chemicals and the mega puck approach (no matter how poor the pool company is!). Assuming my cya drops again during next winter, this seems a reasonable approach to recuscitation in the spring.
Thanks again