This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
I have no personal experience of its use in these diseases, but benefit has been reported from it. In early stages it is said to improve digestion, in later stages to relieve dyspnoea, and in struma to cause absorption of glandular swellings (Ranking, 1868).
In these conditions generally, phosphoric acid fulfils many indications as a grateful moderately astringent tonic; it relieves hoarseness and dry irritating cough accompanied by pain and laryngeal soreness. Dr. Cotton gave it to twenty-five patients with chronic uncomplicated phthisis at Brompton Hospital, and observed benefit in a few advanced cases: it improved appetite and controlled secretion, although sometimes nausea and pain were excited: he could not trace a specific effect from it, but rather the action of a general nerve-tonic; it acted specially well combined with iron (Medical Times, i., 1863). Dr. C. J. B. Williams recommends it with cod-liver oil (Lancet, ii., 1868, p. 213).
In the dyspepsia so common in phthisis, it is also useful, relieving the pain, sickness, and diarrhoea which occur after meals. Profuse night-sweats and other exhausting discharges are controlled by it, and it exerts a sedative effect upon the excessive sexual desire which often developes in some stages of phthisis. Dr. Todd used it in cardialgia.