NOVELTY - Making an iron crosslinker comprises: forming a substantially uniform mixture of ingredients (in active parts by weight) comprising ferric sulfate (30-33.6) containing 0.8-1.3 wt.% of sulfuric acid, citric acid (10-50), monoisopropanolamine (8.9-10), and ammonium hydroxide (3.1-3.6); dissolving ferric ammonium citrate (red or brown) (3.8-4.5 parts by weight); and mixing sodium cumene sulfonate (4.25-4.8 parts by weight), where an exothermic reaction is effected in the mixture.    USE - The method is useful for making an iron crosslinker which is useful: in hydrocarbon gel formation at temperatures lower than -20 degrees C; and for forming an liquefied propane gas hydrocarbon gel that is used in fracturing subterranean formations (all claimed).    ADVANTAGE - The method: provides liquefied propane gas hydrocarbon gel formation which is substantially free of water; can be carried out at very low temperatures without using either glycerin or sorbitol; and provides gel systems that achieve desirable viscosity within an appropriately short period.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a composition useful for forming gels in liquefied propane, comprising (in parts by weight) the reaction product of ferric sulfate (57-63.5), ferric ammonium citrate (red or brown) (4.37-4.83), citric acid (11.4-50), ammonium hydroxide (12.06-13.33) and monoisopropanolamine (10.07-11.13);    (2) forming an liquefied propane gas (LPG) hydrocarbon gel comprising: injecting 0.5-5 wt.% of a diester of at least one of 2-5C alcohol and an amine polyphosphate which is a reaction product of a trialkyl phosphate of formula (O=P(OCxH(2x+1))3) with phosphoric acid, into an LPG base; and mixing 0.5-5 wt.% of the iron crosslinker into the LPG;    (3) a low temperature hydrocarbon gel composition comprising: a liquefied propane; a phosphate ester gel former; and the iron crosslinker for the phosphate ester gel former comprising the composition; and    (4) fracturing an underground formation through a well, comprising fracturing the formation by introducing a gelled fracturing composition of the low temperature hydrocarbon gel composition into the well under pressure sufficient to fracture the underground formation, at a temperature lower than -20 degrees C.    x = 2-5.