Iron(III) pyrophosphate is an inorganic chemical compound with the formula Fe4(P2O7)3. Synthesis
Anhydrous iron(III) pyrophosphate can be prepared by heating the mixture of iron(III) metaphosphate and iron(III) phosphate under oxygen with the stoichiometric ratio 1:3. The reactants can be prepared by reacting iron(III) nitrate nonahydrate with phosphoric acid.It can be also prepared via the following reaction:
3 Na4P2O7(aq) + 4 FeCl3(aq) → Fe4(P2O7)3(s) + 12 NaCl(aq)

References
External links
"Ferric pyrophosphate". Drug Information Portal. U.S. National Library of Medicine. "Ferric pyrophosphate nonahydrate". Drug Information Portal. U.S. National Library of Medicine. "Ferric pyrophosphate citrate". Drug Information Portal. U.S. National Library of Medicine.
Macrogol, also known as polyethylene glycol (PEG), is used as a medication to treat constipation in children and adults. It is also used to empty the bowels before a colonoscopy. It is taken by mouth. Benefits usually occur within three days. Generally it is only recommended for up to two weeks. It is also used as an excipient.Side effects may include increased bowel gas, abdominal pain, and nausea. Rare but serious side effects may include an abnormal heartbeat, seizures, and kidney problems. Use appears to be safe during pregnancy. It is classified as an osmotic laxative. It works by increasing the amount of water in the stool.Macrogol came into use as a bowel prep in 1980 and was approved for medical use in the United States in 1999. It is available as a generic medication and over the counter. In 2018, it was the 163rd most commonly prescribed medication in the United States, with more than 3 million prescriptions. Typically it is formulated together with electrolytes. Medical uses
Constipation
Macrogol 3350, often in combination with electrolytes, is used for short-term relief of constipation as well as for long-term use in constipation of various causes, including in multiple sclerosis and Parkinsons disease patients (an often-overlooked non-motor symptom) as well as constipation caused by pharmaceutical drugs such as opioids and anticholinergics. Whole bowel irrigation with macrogol is part of the bowel preparation before surgery or colonoscopy.