(This post is a duplicate of this post at the Pool 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

............................................................................... 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

Thanks,
Richard

I did some measurements today. I got (in g/ml):

Calcium Chloride Dihydrate . . . 0.837
Cyanuric Acid . . . . . . . . . . . . . 0.765
Dichlor granules . . . . . . . . . . . 0.985
Borax . . . . . . . . . . . . . . . . . . . 0.757

These numbers were repeatable to about +-1%. Of the four borax was by far the most variable. I could easily pack it down into a smaller volume and fit more in if I wanted to. The number above is from taking a scoop and filling it in the obvious way out of a large container and then scraping the excess off the top.

Thanks Jason. I've updated the table accordingly. I think the MSDS number for Calcium Chloride Dihydrate must have been for the actual product, not for absolute solid, since it pretty much matched what you measured and what I've roughly found so I've changed the "solid" number to "?" since it's probably higher. The CYA and Dichlor I used as is. I added your 20 Mule Team Borax number, but the number I had was from my own measurements and was denser by quite a bit so either there's a lot of variation or I tapped the measuring cup I used more (it seems to settle a lot). So both numbers are in the table.