Phenolphthalein pH Indicator 1% Solution — One 500 mL (1.06 Pint) Bottle Plus 1 Dropper Bottle containing 50 ml of Solution

Biopharm replaced this (free) with different formula turns red in acid and looses color as acidity is used up descaling heating coils. This product works opposite red in basic solution. Call them and get the right stuff for this application. When the vinegar looses red color all the acid is consumed and needs replaced until remains red meaning all scale have been removed from heat transfer coils. I have apartment and office buildings with several Rennai tankless water heater need vinegar pumped through coils yearly to descale and keep efficient. You can buy expensive pre-colored red vinegar or for a fraction cost use this.

I am a science teacher and I used this for pH testing. For those who have written reviews previously, the solution is SUPPOSED to turn pink in an alkaline. It remains clear in acids and neutrals. This product was exactly what I needed for our experiments.

I was very impressed with the quality of the product and the company's attention to detail by providing documentation on how to use it. I manufacture natural liquid hand soap and use Phenolphthalein to test for excess lye. I also liked the second bottle (which also contained Phenolphthalein) and dropper that came with it, it saved me the time and money of not having to buy a dropper. I would definitely buy this product again.

I purchased this to monitor the status of the soap that I make. It works for other things as well. It came with directions which were quite handy, as I was not certain how to use it. The size is large and I won't need to purchase additional for some time. It arrived fast and in good condition. I am glad I purchased this.

Big bottle that should last a loooooong time! I like also that it came with a smaller bottle with a dropper for easier handling.

I hadn't noticed that the solvent is propylene glycol until I received it. So, not the same thing we used in chemistry class but the solute is what matters! This was well packaged, and the manufacturer obviously put thought into how the consumer would use it -- the cap to refill the dropper bottle, etc. -- which is much appreciated. I would recommend keeping the stock bottle, which is colorless translucent HDPE, in a cool, dark place. Overall, very satisfied. I'd buy this again when needing a restock.

Have used this product before, this was a reorder. Extremely reliable product. Secure packaging. And works perfectly for a safety test in my line of work (identifying caustic). Will order from Biopharm every time!

Product appears exactly as advertised. A little bit of residue was in the dropper, but it was harmless and easily cleared out. Good quality materials and works for my application.

Ordered this because of the low relative cost, quick shipping time relative to other providers. Product ended up taking an extra month to arrive. Product seems to work as described. Used for dyeing concrete.

Great!