Question
Posted on: March 6 2013Precipitation in mouth rinse agent with bicarbonate after borate 30g after bicarbonate 20g mint spiritus 10g Aqua AD 600ml
A fixed lump appears underneath the bottle-however Solubilities OK
Answer
(Thanks to the collaboration of Apoth. A-S De Backer)
In Such A case, we must always be suspicious of the solubility. After borate is soluble 1 in 16ml of water, while bicarbonate 1 in 11ml water. This means for 30g borax 480ml water and for bicarbonate 220ml water. Being together 700ml of water. I know this is a peculiar method of calculating size yet let them suspect that perhaps a solubility problem can pop up.
The addition of glycerin prevents precipitation. But we have to take into account the reaction that occurs between glycerin and borax and which gives rise to the formation of boroglycerine, which, depending on the amount of glycerin, is the solution. This acid reaction is obviously incompatible with bicarbonate! We have to do here with a 5% borax solution, which under the influence of 10% glycerin has a pH = 7.5. This is acceptable for the after bicarbonate. On the limit, the addition of 15% glycerin is also acceptable. Without adding glycerin is the pH of a 5% borax solution = 9.3.
In Such A case, we must always be suspicious of the solubility. After borate is soluble 1 in 16ml of water, while bicarbonate 1 in 11ml water. This means for 30g borax 480ml water and for bicarbonate 220ml water. Being together 700ml of water. I know this is a peculiar method of calculating size yet let them suspect that perhaps a solubility problem can pop up.
The addition of glycerin prevents precipitation. But we have to take into account the reaction that occurs between glycerin and borax and which gives rise to the formation of boroglycerine, which, depending on the amount of glycerin, is the solution. This acid reaction is obviously incompatible with bicarbonate! We have to do here with a 5% borax solution, which under the influence of 10% glycerin has a pH = 7.5. This is acceptable for the after bicarbonate. On the limit, the addition of 15% glycerin is also acceptable. Without adding glycerin is the pH of a 5% borax solution = 9.3.