This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Many bottlers are accustomed to prepare their syrups by boiling, filtering and adding while still hot or warm the fruit-acid solution. This is quite erroneous. Either add the fruit acid before boiling, or after the syrup has become quite cold, as the warm syrup is slowly inverted, or is starting conversion, which is continued within the bottled beverage, causing all those changes previously stated.