Guar gum needs to be thin enough to make it easier to pump. Then as it flows down the pipe, the fluid needs to gel up to support the proppant and flush it deep into the fractures. After that process, the gel has to break down so we can flow back and recover the fracking fluid, but leave the proppant behind. This requires a chemical process which produces then breaks the gel cross-linking at a predictable rate. Guar+boron+proprietary chemicals can accomplish both of these goals at once. Guar gum retards ice crystal growth nonspecifically by slowing mass transfer across the solid/liquid interface.
Hydrochloric acid (roughly 20.2%) can be used as a primary standard in quantitative analysis, although its exact concentration depends on the atmospheric pressure when it is prepared. Hydrochloric acid is frequently used in chemical analysis to prepare ("digest") samples for analysis. Concentrated hydrochloric acid dissolves many metals and forms oxidized metal chlorides and hydrogen gas. It also reacts with basic compounds such as calcium carbonate or copper(II) oxide, forming the dissolved chlorides that can be analyzed. Physical properties of hydrochloric acid, such as boiling and melting points, density, and pH, depend on the concentration or molarity of HCl in the aqueous solution.