As I stated previously, glycin is only slightly soluble in water.Originally Posted by titrisol
Glycin is quite soluble in alkaline solutions. In order to dissolve glycin in water, you need to make the water alkaline. Sodium (or potassium) sulfite will perform this function, - so will carbonate and other alkalis.
However, if you are mixing a developer (dissolved in water) that uses both metol and glycin, the metol should be dissolved first. It is important to add no more than a pinch of sulfite before dissolving the metol. If there is too much sulfite, a large percentage of the metol may become insoluble. After the metol is dissolved, add the remaining sulfite, then add the glycin.