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jeff5may · 02-25-16, 10:54 AM

The sodium acetate looks like it would be the most suitable material for your temperature range. It is a fairly common salt by chemical supply standards. Not highly expensive in bulk, nontechnical grades.

Food grade, bulk anhydrous:
Sodium Acetate

Runway ice melt:
Sodium Acetate MSDS | MeltSnow.com

The lab or reagent grade is much more expensive, and actually will work worse for your application. The ultra-pure stuff doesn't have anything in it to help seed the crystallization when the temperature drops. That's how those little "hot hands" bags stay liquid until you pop the little disc inside of them. The phase change occurs on demand due to the mechanical shock induced. A little bit of impurity in the salt will help confine the phase change within your target temperature range. I am sure this has been researched thoroughly by chemists, and various custom formulations could be found with datasheets and patents and such to support the respective products. As always, the more specific the application, the higher the product price rises. I don't know if the more inexpensive premixed solutions available on ebay or amazon would have trace chemicals in them to help stabilize the phase change temperature range or not.

You can make small, crude batches of it by mixing white vinegar and baking soda. This chemical reaction yields weak sodium acetate and carbonic acid if there is excess vinegar. Adding extra baking soda yields nothing, which is undesirable. When boiled to increase the concentration, the extra carbonic acid breaks down into co2 and leaves the solution. If using grocery store grade chemicals, the acetate salt must be crystallized, ground, and rinsed with rubbing alcohol to remove the contaminants in the vinegar to refine the salt. This still leaves trace amounts of who knows what, depending on filtering and rinsing methods, but there seems to be lots of youtube videos, instructables, and blogs from home chemists trying their luck to watch.

Crystallization of homemade sodium acetate - All

Please fill us in on anything you find out about this application. I saw lots of building products being marketed, but most were formulated so the phase change occurs between normal room temperature and body temperature in range.

02-25-16, 10:54 AM	#16
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	The sodium acetate looks like it would be the most suitable material for your temperature range. It is a fairly common salt by chemical supply standards. Not highly expensive in bulk, nontechnical grades. Food grade, bulk anhydrous: Sodium Acetate Runway ice melt: Sodium Acetate MSDS \| MeltSnow.com The lab or reagent grade is much more expensive, and actually will work worse for your application. The ultra-pure stuff doesn't have anything in it to help seed the crystallization when the temperature drops. That's how those little "hot hands" bags stay liquid until you pop the little disc inside of them. The phase change occurs on demand due to the mechanical shock induced. A little bit of impurity in the salt will help confine the phase change within your target temperature range. I am sure this has been researched thoroughly by chemists, and various custom formulations could be found with datasheets and patents and such to support the respective products. As always, the more specific the application, the higher the product price rises. I don't know if the more inexpensive premixed solutions available on ebay or amazon would have trace chemicals in them to help stabilize the phase change temperature range or not. You can make small, crude batches of it by mixing white vinegar and baking soda. This chemical reaction yields weak sodium acetate and carbonic acid if there is excess vinegar. Adding extra baking soda yields nothing, which is undesirable. When boiled to increase the concentration, the extra carbonic acid breaks down into co2 and leaves the solution. If using grocery store grade chemicals, the acetate salt must be crystallized, ground, and rinsed with rubbing alcohol to remove the contaminants in the vinegar to refine the salt. This still leaves trace amounts of who knows what, depending on filtering and rinsing methods, but there seems to be lots of youtube videos, instructables, and blogs from home chemists trying their luck to watch. Crystallization of homemade sodium acetate - All Please fill us in on anything you find out about this application. I saw lots of building products being marketed, but most were formulated so the phase change occurs between normal room temperature and body temperature in range.