# Chemical Forums

## Specialty Chemistry Forums => Other Sciences Question Forum => Topic started by: Watcher778 on October 18, 2020, 03:20:30 AM

Post by: Watcher778 on October 18, 2020, 03:20:30 AM
I need a professional. After looking this up online, I get anywhere from 2 tsp to 14 tbsp. That is a big difference. I have 99% calcium hypochlorite. 70% available CL. How much do I use to make 1 gallon of 5% bleach? If I end up having to use it I want to be sure I have the correct strength. I do have a small scale if the answer is easier by weight. Thanks.
Title: Re: Question about making bleach.
Post by: Borek on October 18, 2020, 04:48:19 AM
Nah, you don't need a professional, this is a high school level stuff - better try to understand how and calculate by yourself.

How much does 1 gallon of water weigh? (5% bleach has a very similar density).

5% of that weigh is how much?

Convert to tbsps, you are done.

Just don't add the solid to 1 gallon of water, dissolve in 3/4 gallon of water and fill up to 1 gal. Not that it matters much with such recipes, but that's the correct way of doing it.
Title: Re: Question about making bleach.
Post by: Watcher778 on October 18, 2020, 01:03:30 PM
See I was thinking that was too easy. Just didn't trust myself. I can definitely do that math.
Thanks

How did you know to use weight and not volume? I mean 5% of the weight of a gallon of water wouldn't be the same as 5% of the volume of whatever I was try mix in, if density was way different. Right? I have been out of school too long and lost what I didn't exercise. And about how to mix. That is so I don't end up with 1 gallon plus 5%, going up to the gallon gets my exactly 1 gallon.
Title: Re: Question about making bleach.
Post by: Borek on October 18, 2020, 01:31:29 PM
Typically concentrations are given in w/w (weight/weight). When it comes to weight/volume things get tricky, especially when you use non-metric units. In SI w/v is reasonably simple and for most cases where approximate concentration is enough grams per 100 mL of water solution (which is how w/v is typically understood) are equivalent to w/w. When it comes to tbsp/gallon things get so convoluted it doesn't make sense to use w/v, as you need some additional conversion factors.

Sorry, I never thought about tbsp as a unit of volume, more like "1 tbsp is about 17g of salt" (actually that's for a kitchen salt, not for calcium hypochlorite, I believe it should still keep you in a right ballpark, although just weighing the hypochlorite would be much better). My bad for no stating that clearly.
Title: Re: Question about making bleach.
Post by: Watcher778 on October 18, 2020, 03:28:57 PM
Thanks a lot for your help. That was just simple enough for me to follow and understand. I get why the forum rules say help them figure it out instead of just giving the exact answer. I would rather understand than just be fed a fish. I don't mind working for it but in my case I forgot all the basics so I didn't really know where to start or how to check myself. I appreciate the help. I can definitely make my own bleach now. 👍