Saturday, September 14, 2013

Weekend Wonderings: Where to get supplies and how to figure out w/v or molarity!

Apparently holiday time means loads of playing in the workshop, but less time working on the blog. I have so much to write, I admit I'm having trouble figuring out where to start. I'm hearing back from my testers about the eye liner sealant gel and I'm waiting to hear from other testers about the eye gels I'm working on (filled with exciting cosmeceuticals!). I'm getting results from them about the Natragem EW lotions as well. Oh, and I'm expeirmenting with different thickeners for surfactant blends, as you can see in the picture. In short, loads of products, not enough time to write about them! Let's take a few moments to look at some of the comments written in the last two weeks!

If you are waiting for a response to an e-mail or comment, I'm getting around to it. I think I'm a month behind on e-mail, and almost two weeks back on comments. If you wrote to me before that time, please feel free to send it again, or watch this weekend for your comment here! As a note, please subscribe to the post in which you've written your comment so you can see if it's been answered. I might not get to it as a Weekend Wondering, but I try to answer every comment that comes in. If you are a business and have written to me asking me to write a formulate for you, I haven't responded because I've asked you not to ask. If you've asked a question, then I just haven't gotten around to it. 

In this post on cyclomethicone, Baron asks: Where did you get Cyclomethicone?

I get mine from Voyageur Soap & Candle or, but if you check the FAQ and scroll down a bit, you'll see there's a list of suppliers from all around the world, and there's bound to be somewhere local to you. I really can't stress enough how much you want to consult those lists because if you ask me where I get my supplies, odds are pretty good I'm going to tell you about a Canadian supplier (and usually it's Voyageur Soap & Candle or Aquarius Aroma & Soap). 

There are tons of reasons to go to the FAQ, but I've included some basics you might want to purchase when you're starting out! 

As well, if you're in Europe, take a look at Eucalypta's list of European suppliers. She did a killer job of putting this together. 

In this post on salicylic acid, Sanziene notes she'll be using salicylic acid with propylene glycol because it's more soluble, but...I have no idea how to read the chart ... I want to dissolve 2% salicylic acid, how much propylene glycol should I use?

You might recall the posts on solubility. (If not, click here and click here.) For solubility we have to consider how soluble something is and whether it's soluble in water, alcohol, oil, and other liquid-y things. If you look at the chart above, we can see that it says % w/v, which means percentage weight to volume. So when we try to dissolve salicylic acid in distilled water, about 0.185% or 0.185 grams dissolves into it. (That's really low!)

I think this is a better chart, although you have to figure out the molarity of salicylic acid.
1.592 M, which means 1.592 moles of salicylic acid dissolves in 1 litre of propylene glycol. A mole of salicylic acid weighs 138.12 grams, which means we can dissolve 219.88 grams of salicylic acid in 1 litre of propylene glycol. (1.592 M x 138.13 grams = 219.88 grams per litre). So we could dissolve 21.988 grams in 100 ml or 2.1988 grams in 10 ml (2 tsp). (I prefer molarity over the whole w/v thing.)

We can dissolve 0.014 moles or 1.93368 grams (let's round to 1.93 grams) in 1000 ml or 1 litre, which works out to 0.193 grams in 100 ml of water, which is almost the 0.185 grams we see in the chart above.

If we compare this to distilled water, we can dissolve 0.185 to 0.193 grams in water and 2.20 grams in propylene glycol. Big difference, eh?

I'll go into moles and molarity later this week on Chemistry Thursday! The short summary is that molarity or M is the number of moles of something divided by volume. I promise all will become clear soon...

Related posts:
Converting percentages to weight

I'm off to teach the kids of Yarrow how to make adorable zippered bags with my mom, so I best shower and get going! See you later with more comments!


melian1 said...

i look forward to the info on solubility and how to read the charts, and how to translate that into our formulas!

melian1 said...

i forgot to mention that in my research, using a mixed solvent approach seems to be yielding better results than any one solvent by itself. it is called (which i'm sure you already know, lol) Solubility using mixed-solvency approach. i copied one study and saved it, but managed to NOT save the url. darn it!

but i did manage to copy this: Keywords: Co-solvents, hydrotropy, mixed-solvency
How to cite this article:
Maheshwari R K. "Mixed-solvency approach" - Boon for solubilization of poorly water-soluble drugs. Asian J Pharm 2010;4:60-3

How to cite this URL:
Maheshwari R K. "Mixed-solvency approach" - Boon for solubilization of poorly water-soluble drugs. Asian J Pharm [serial online] 2010 [cited 2013 Jun 24];4:60-3. Available from:
which i'm hoping can point you to the whole thing.

Sânziene şi Mătrăgună said...

wow, Susan, this is just great!! <3 thank you so much for the very clear explanation!! :)

Seb NGuyen said...

Hi Susan! I try to make this 1% SA solution and it creates some floating clouds and curdling. My recipe:
1g SA
2g Glycerin
10g Alcohol 99,5%
20g Witch Hazel
When I added SA to glycerin and Alcohol, it works well, dissolve completely. However when I added water or witch hazel, tiny powders appeared. Stirring didnt help much and then, clouds happened and curdling came.

Could you help me to point out why?
One more question is that I found out SA is oil soluble as well (look at Herbarie or PMS I think), could I just add SA to my oil and use it anyway?
Thanks a bunch.

Susan Barclay-Nichols said...

Hi Seb. Salicylic acid isn't oil soluble. Check out this post for more information. I also encourage you to read the chart linked in that article for more information.

As a note, when you are posting recipes, can you please post your process? I have no idea what process you followed, whether you heated or held, and I can't make comments on what you've done if you don't include all the information.

Seb NGuyen said...

Hi Susan. Thank you for replying my comment. Firstly I add SA to Alcohol and Glycerin, mix it well. Then I add Water and very tiny things start happening. A few minutes later, clouds or curdling appears even I tried to mix it hard.
However I found out the reason. It might be because of PH of the mixture. When i added a little Sodium Lactate, the curdling starts disappearing.
Thanks Susan. About Salicylic acid is oil soluble or not, I found it here:

And when I tested adding a little to a mixture of oil, it seems to be dissolved better than in water. Hope you can give me more information if possible. Sorry if this bothers you much.