how many times can you calibrate with one bottle?

If you're using a combination pH electrode rinse the electrode well with distilled water to remove storage solution or whatever the electrode was previously in. Then rinse the electrode with a small amount (about 25 ml) of the buffer. Throw away the rinse and add fresh buffer to cover the electrode well (25 to 50ml, depending upon how big your electrode is ). If you're using a separate reference electrode you may need a larger volume to cover both electrodes well. Swirl the electrode(s) in the buffer and let the reading stabilize. Normally you start with pH 7 and set that calibration point then repeat the process using pH 4 and use the "slope" adjustment to set this point. Do not pour the used buffer back into the buffer bottle; throw it away. You risk contaminating your reference standard by trying to reuse it. Depending upon the size of your electrode(s) you may need 50 ml to 100 ml each time to do a good calibration. So the shorter answer is probably 3 to 5 calibrations per 8 oz bottle. It is good practice to calibrate the same day you are measuring your sample(s) because the meter/electrode settings can "drift" out of calibration. If you do pH measurements often you may want to buy the 500 ml (pint) size calibration kit.

I use the storage solution for my hm digital ph tester and I later get salt deposits on the lid, is this storage solution ok for this electrode?

Yes it is OK. Because the storage solution has a lot of potassium chloride dissolved in it crystals will form where the water has evaporated away. You can wipe them away with a damp paper towel or simple ignore them. They will not cause any problem.

I have a hm digital ph tester, how do i use the 4.0, 7.0 calibration solutions? do i dilute it or use it as is?

Do not dilute it. Pour a small amount (approx. 50 ml) into a small clean, dry beaker (or glass or jar). For highest accuracy you should know the temperature of the solution (ideally 25 deg. C). You really need a good thermometer for accurate work. Your unknown sample should be adjusted to 25 deg also at the time of measurement. You can warm the sample to 25 deg. C by holding it against your warm skin for a while if it's within a few degrees of 25. If the sample is really cold try 5 or 10 seconds in a microwave oven. If you over do it just wait until it cools back to where you want it. Start with the pH 7 standard and immerse the pH electrode in the small calibration sample and follow the instructions provided by your meter manufacturer. Do NOT return the used buffer to the original bottle as this will ruin the integrity of the original standard. Throw it away. The original bottle will be good for a year or more if handled properly.

pH Buffer Calibration Solution 3-Pack: pH 4.00 Buffer, pH 7.00 Buffer, and Electrode Storage Solution — 250 mL (8.4 fl oz) Each — NIST Traceable Reference Standards for All pH Meters

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