Freeze drying and dehydrating potatoes has a very minimal effect on solanine content. Common dehydrating agents used in organic synthesis include sulfuric acid and alumina. It is a powerful desiccant and dehydrating agent. Consuming alcohol may also lead to orthostatic hypotension due to its dehydrating effects. During slow cooling, ice forms extracellularly, causing water to osmotically leave cells, thereby dehydrating them. Dehydrating and hydrogenating cumyl alcohol recycles the cumene. Alcohols and acetones are also dehydrating agents. The anhydrous salt is used as a dehydrating agent for forming and manipulating acetal groups. It can be produced by dehydrating benzoic acid by heating. Marzipan must be covered in an airtight container to prevent it from hardening and dehydrating. The anhydrous material is a powerful dehydrating agent. Extreme acidity, heat, and dehydrating conditions are usually required. It can also be prepared by dehydrating fructose. The principal use is as a dehydrating agent in the preparation of concentrated nitric acid. This is made by preparing tea and then dehydrating it, similar to instant coffee.