Thickeners include sodium alginate, carrageenan, gelatine, sodium bicarbonate, tetrasodium pyrophosphate, and alginic acid. Guar gum has synergistic effects with locust bean gum and sodium alginate. Cochrane reviews summarise evidence on alginate dressings , foam dressings , and hydrogel dressings. Sodium alginate is the sodium salt of alginic acid. Propylene glycol is also present in propylene glycol alginate, which is known as E405. Dental impression material uses alginate as its means of gelling. Collogel dispersed sodium alginate in domestic water systems. Propylene glycol alginate (PGA) is an emulsifier, stabilizer, and thickener used in food products. Another plant-derived mucilage is made from sodium alginate. To the sodium alginate from the initial extraction solution, a calcium salt is added. A solution of 5% sodium alginate has been used. The goal of the extraction process is to obtain dry, powdered, sodium alginate. Alginates are used in wound dressings (see alginate dressing), and dental moulds. Blended power of Chitosan along with alginate are used together to form functional wound dressings. None of the usual seaweeds for alginate production are cultivated.