You can make up a liquid KH booster. The amounts depend on what your'e using, the size of the tank, the dose size and the solubility of the chemical.
I have several listed in my Windows calculator
if you don't want to do the calculations yourself.
Amount of each to raise one gallon of water 1 dKH
KHCO3 135.045657592 mg Solubility @ 20 °C: 337g/l
K2CO3 93.212947875 mg Solubility @ 20 °C: 1,110g/l
NaHCO3 21.761702144 mg Solubility @ 20 °C: 96g/l
Example, Lets say you have a 10 gallon tank. You want to raise KH 2 dGH. Using a 1 liter bottle, a dose size of 30ml and K2CO3...
93.212947875 * 2 = 186.42589575 mg to raise 1 gallon 2 degrees
186.42589575 * 10 = 1,864.2589575 mg to raise 10 gallons 2 degrees
So one dose is 1,864.2589575 mg
1,000 ml / 30 ml = 33.333 doses in one liter
33.333 * 1,864.2589575 = 62,141 mg
Check solubility. 62.141 grams is 1,110g/l so your'e all set.
Add 62.141 grams to your 1 liter container and dose at 30 ml per 10 gallons to raise KH 2 dKH
btw, Solubility was obtained from a solubility table
. No math involved