Background
The value of the sugar acids and their soluble salts and lactones as sequestering or chelating agents for metal ions, particularly in alkaline solutions, has been recognized for many years. These materials have been used industrially in alkaline de-rusting processes, bottle washing, descaling, for the prevention of iron-staining in paper making, and in the processing of cotton and other textiles, among numerous other applications which could be mentioned. Soil gluconates, particularly sodium gluconate, have become the most widespread use for these purposes, primarily because of their availability and relatively low cost. Kiliani prepared sodium glucoheptonate as early as 1886 by the reaction of hydrocyanic acid with glucose in an aqueous solution, and many modified methods for the preparation of the valuable salt have been suggested. However, it is available only in highly coloured amber to red or red-brown solutions. Such highly colored sequestering agents are unsuitable in many applications in the paper, textile and pharmaceutical industries.
Uses
Sodium glucoheptonate is used for cleaning metal, mercerizing, paint stripping, and aluminum etching. It is also used to mercerize cotton, linen, hemp, and other plant-based fibers to increase strength and add luster to their overall appearance of threads and fabrics.
Synthesis
98 g (2 mol) of sodium cyanide and 300 g of water were charged into a flask fitted with a stirrer, thermometer and a connection to a water jet aspirator. The contents of the flask were cooled to 2 ℃. using an ice bath. 396 g (2 mol) of dextrose hydrate were charged into the flask over about 30 minutes. When the sugar had all been charged, the temperature rose to 8 ℃., when the vacuum jet was turned on to provide a vacuum of about 40 mm of Hg. Within about 30 minutes, the temperature rose to 27 ℃., when the ammonia began to boil off vigorously. Within approximately 1 hour, the alpha sodium glucoheptonate dihydrate began to crystallize. The removal of the ammonia was continued at 27 ℃ and a vacuum of 33-40 mm of Hg for 6 hours. The crystals were filtered, water washed, and air dried. The first crop yield of alpha sodium glucoheptonate was -328 grams or 57.7% of the theoretical.
