Sodium Acid Pyrophosphate (SAPP) is an inorganic compound with the formula Na2H2P2O7. Here is a description of disodium hydrogen pyrophosphate and some common uses:

Description: 

•Physical properties: Disodium hydrogen pyrophosphate is a white crystal or powder, soluble in water.

•Chemical properties: Disodium hydrogen pyrophosphate is a dibasic salt of pyrophosphate and has acidic properties.

Purpose: 

1. Food industry: Disodium hydrogen pyrophosphate is widely used in the food industry as a food additive. It is often used as an acid regulator, starter and buffer. Disodium hydrogen pyrophosphate is commonly used in baked goods to regulate pH, increase the leavening of dough and improve the texture of food. It is often added to bread, cakes, cookies, baking powder, instant food and other products.

2. Meat industry: Disodium hydrogen pyrophosphate is also used in the meat industry. It is often used as an expansion agent and water retention agent for meat products, which can improve the taste of meat and maintain the wetness of meat products.

3. Industrial applications: Disodium hydrogen pyrophosphate also has some applications in industry. It is used as a metal surface treatment agent for rust and corrosion prevention. In addition, disodium hydrogen pyrophosphate can also be used in water treatment to soften water and prevent the formation of scale.