He was appointed in 1795, promoted later to be chief of his department, and retired on a pension in 1850, when his services received official acknowledgment.
[1] His subordinate at the Tower, John Hewitt, was encouraged to take an interest in the national collection of arms and armour there, and produced a pioneering guide.
[9] He examined the properties of the acid, and showed that it can easily be oxidised by the air, Prussian blue being formed at the same time; this observation was later utilised in dyeing.
[10] Porrett in 1813 made experiments with Rupert Kirk and William Wilson on the dangerous substance chloride of nitrogen.
[1] The following is a list of Porrett's scientific papers:[1] In Nicholson's Journal: In Philosophical Transactions: In Thomson's Annals of Philosophy: In the Chemical Society's Memoirs: This article incorporates text from a publication now in the public domain: "Porrett, Robert".