Mainly due to the different base of salt caused. The appearance of PAC is related to the basicity of the salt, the manufacturing method, the content of impurities and the content. Pure liquid PAC solution, when the basicity of the salt is in the range of 40% -60%, is a light yellow transparent liquid, and when it is above 60%, it gradually becomes a colorless and transparent liquid. Solid aluminum chloride, the base degree of 30% or less when the lens, 30% to 60% in the case of jelly, 60% or more gradually become glassy or resinous. Polyaluminium chlorides made from bauxite or clay ore are yellow to brown transparent liquids. Alkalinity is a relatively important indicator of PAC, especially for PAC grade drinking water, which is one of the most important indicators for the control of the production of poly aluminum lines. Salt base lower, the higher the price, the buyer can plant according to the actual situation to operate. In addition, different raw materials, different processes of production and processing of PAC products, the basic degree of salt is different, which requires manufacturers to be adjusted. Improve the base product of PAC, can greatly improve the economic benefits of production and use. Salt base from 65% to 92%, the cost of raw materials can be reduced by 20%, the use of cost can be reduced by 40%.