Potassium bitartrate, also known as potassium hydrogen tartrate, has formula KC4H5O6. It is a byproduct of winemaking. It is also known as cream of tartar. It is the potassium acid salt of tartaric acid.
Potassium bitartrate crystallises
in wine casks during the fermentation
of grape juice
. In wines bottled before they are fully ripe, it can precipitate
on the side of the bottle in a sort of crust, thus forming what is called "crusted wine
This crude form (known as beeswing) is collected and purified to produce the white, odorless, acidic powder used for many culinary and other household purposes.
In food, potassium bitartrate is used for:
A similar acid salt, sodium acid pyrophosphate, is confused with cream of tartar due to their similar function in baking powder.
Can be used with white vinegar to make a paste-like cleaning agent.
Potassium acid tartrate, also known as potassium hydrogen tartrate, and according to NIST
, is also used as a primary reference standard for a pH buffer
. Using an excess of the salt in water, a saturated solution
is created with a pH
of 3.557 at 25°C. Upon dissolution in water, potassium bitartrate will dissociate
into acid tartrate, potassium cation, and the tartrate dianion
. Thus, a saturated solution creates a buffer with standard pH. Before use as a standard, it is recommended that the solution be filtered or decanted
between 22° and 28°C.