SureHennie, I was wondering if you could possibly give us a short list of "generic" alternatives to the more expensive Branded Chemicals?
I have used this many times in the past to check if my digital pH controller's calibration is correct, and I too, like Dr. Bingman, have found that there are some pretty inaccurate calibration standards on the market - try this recipe, and have some peace of mindA number of aquarists were reporting some very strange pH values from freshly calibrated pH monitors. They tended to be much higher than expected. There was a common thread in these stories: All of them had used a certain brand of pH 10 calibration solution. So, I went to my local pet store, bought some of this product and found that it was low by nearly one pH unit when checked with a research-quality pH meter and electrode, calibrated with fresh research-quality pH standards!In response, I proposed that people at least check their calibrations with another easily obtainable pH standard, a simple solution of borax dissolved in water.
Why can borax be used to make a pH standard? All of the NIST pH calibration solutions (the pH 4.0, 7.0 and 10.0 calibration solutions that you might buy from a scientific supply house) are made by mixing controlled quantities of an acid and conjugate base. So usually you would need to mix precise quantities of two different compounds to make a pH standard solution. However, borax has a very special property. It can be regarded as an equimolar mixture of boric acid and borate ions (with the required counter-ions and water of hydration.) So, within its crystalline structure, it has both components required to make a pH standard solution. Better still, it carries both of them in precise quantities, because if it doesn’t, it really can’t be borax.
To make the textbook standard sodium metaborate, you dissolve 3.8 grams of borax per liter of purified water. Most of you don’t have access to an accurate balance, so it won’t be simple to follow that formulation. However, it turns out that 1/2 teaspoon of solid borax weighs just about two grams (see Table). It also turns out that the pH of borax solutions is only weakly dependent on the concentration of borax in the solution. So, we don’t need to be tremendously precise in our measurement of the borax to still produce a useful pH standard.
Because 1 quart = 946.4 milliliters (ml), if we use a pint of water and add a half teaspoon of borax to it, we should have a pH standard solution with 2 grams of borax per 473 ml or 4.3 grams of borax per liter. This is within about 10 percent of the standard borax pH calibration solution, and because of the weak dependence of pH on concentration, it is close enough for our purposes. So, you should be able to use everyday kitchen measuring equipment to make this solution.
[SIZE=-1]pH of Sodium Metaborate Standard Solution at Various Temperatures
(3.80 grams Na2BO7 10H2O/liter)
[SIZE=-1]Temp - [/SIZE][SIZE=-1]pH[/SIZE]
[SIZE=-1]0[/SIZE][SIZE=-1]°C[/SIZE] - [SIZE=-1]9.464
[/SIZE][SIZE=-1]5[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.395
[/SIZE][SIZE=-1]10[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.332
[/SIZE][SIZE=-1]15[/SIZE][SIZE=-1]°C -[/SIZE][SIZE=-1] 9.276
[/SIZE][SIZE=-1]16[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.266[/SIZE][SIZE=-1]
17[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.256
[/SIZE][SIZE=-1]18[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.245
[/SIZE][SIZE=-1]19[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.235
[/SIZE][SIZE=-1]20[/SIZE][SIZE=-1]°C -[/SIZE][SIZE=-1] 9.225
[/SIZE][SIZE=-1]21[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.216
[/SIZE][SIZE=-1]22[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.207
[/SIZE][SIZE=-1]23[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.198
[/SIZE][SIZE=-1]24[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.192
[/SIZE][SIZE=-1]25[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.180
[/SIZE][SIZE=-1]26[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.172
[/SIZE][SIZE=-1]27[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.167
[/SIZE][SIZE=-1]28[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.155
[/SIZE][SIZE=-1]29[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.147
[/SIZE][SIZE=-1]30[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.139
[/SIZE][SIZE=-1]35[/SIZE][SIZE=-1]°C -[/SIZE][SIZE=-1] 9.081
[/SIZE][SIZE=-1]40[/SIZE][SIZE=-1]°C -[/SIZE] [SIZE=-1]9.068[/SIZE]
How do you use these borax solutions? Well, they have a variety of uses. First, they can be used to check a calibration that has been performed with pH standard solutions that you have obtained elsewhere. You calibrate your system, allowing it to equilibrate at both set-points, and then use a freshly mixed borax standard solution to check that calibration. You can easily spot gross errors in calibration this way.
The borax solutions can be used in a second way: To replace the high pH standard solution. For this purpose, it would be best to use reagent-grade sodium metaborate, but you can use grocery store borax at the cost of perhaps slightly degraded accuracy. There is a motivation to do this. The pH 7.0 standard solution is much more stable than the pH 10.0 standard solution, which rapidly absorbs CO2 from the air with a corresponding decrease in the pH of the standard solution.
Only if you keep it dry and in an air-tight container (the same goes for commercial products...). I've found that if sealed properly the powder stays "good" for at least 2 weeks - don't know about keeping it for longer periods, as it's used up by then.Once done will the bicarb stay, washing soda
Any more news on this Jacques, or the other Gurus, as I would definately up my Iodene and to buy the Red Sea Version, works out way too expensive for my liking...OK -
I buy Alpha concentrated Iodine Tincture from a chemist (50ml bottles). I have a previously used 250ml Iodine bottle (was commercially available iodine). I use one complete bottle of iodine (50ml) and add to that 200ml's of RO water.
I then dose every 2nd or 3rd day, +-35 to 50ml's of diluted iodine to my tank (I add it into the last compartment of my sump where my return pump is. Typically, this compartment holds about 40 litres of water
Am I misreading? or are you adding the epsom salt and bicarb directly to your water? I.e. not dissolved in ro first?I doze into the 3rd chamber of my sump (my chemical filtration chamber)..... This means that the sodium bicarbonate and epsom salts have time to slowly dissolve into the water, long before it reaches my display tank....
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