# Dictionary of National Biography, 1885-1900/Mercer, John

1904 Errata appended.
​MERCER, JOHN (1791–1866), calico-printer and chemist, was born on 21 Feb. 1791 at Dean, in the parish of Great Harwood, near Blackburn. His father, Robert Mercer (whose family had been established in the district for at least 250 years), was at the time a hand-loom weaver; he soon after gave up this occupation and took a farm in the neighbourhood of Great Harwood, where John passed his early years. In 1800 Robert Mercer died, leaving his wife and family with small means; at the age ​of nine John became first a bobbin-winder, and then a hand-loom weaver. At ten a workman in a print-works taught him reading, writing, and arithmetic. He also learnt to play on several instruments, and gave much time to music, to which he remained keenly sensitive through life. When he served as a militiaman, a few years later, he was known as ‘Awkward John,’ and he was transferred to the band. In 1807 his future career was decided by seeing on his infant half-brother a dress of an orange-colour, which ‘set him all on fire to learn dyeing.’ He straightway bought all the dyeing materials he could procure, and, having by a long series of experiments learnt to dye in most colours, he set up in partnership with a man who had suitable premises, and they ‘dyed for Great Harwood and the surrounding country;’ the material operated on consisting chiefly of the remnants which were at that time the perquisites of the hand-loom weavers. In September 1809 Mercer gave up this business, despite its success, to become an apprentice in the colour-shop of the Oakenshaw print-works on the invitation of the owners, Messrs. Fort Bros. But the jealousy of a foreman prevented him from acquiring any real knowledge of the processes employed; and he therefore, in the following year, accepted the surrender of his indentures offered by his masters, who were forced by commercial distress, due to the Berlin decrees, to reduce their staff. Mercer again became a hand-loom weaver, and invented many ingenious designs in weaving. He also gave much attention to the study of mathematics, in which he was helped by an excise surveyor named Lightfoot. In 1813 he became deeply religious and joined the Wesleyans. In the same year he became engaged to Mary Wolstenholme, whom he married on 17 April 1814.
In 1813 Mercer had resumed work as a dyer, while still continuing to weave, and in 1814 his attention was directed towards chemistry by the ‘Chemical Pocket-Book’ of James Parkinson, which ‘introduced him [he writes] into a new world.’ It was this book which led him to his first discovery of importance, a method of fixing orange sulphide of antimony on cotton-cloth; no good orange dye suitable for calico-printing having been previously known. The details of the process were communicated to a firm of printers, and successfully applied, but Mercer received no reward for his services. In 1818 Messrs. Fort Bros. re-engaged Mercer, this time as a chemist in their colour-shop, at a salary of thirty shillings a week. In 1823 Mercer rediscovered and introduced into England a method of applying to cotton-cloth lead chromate, a yellow dye of great importance, originally discovered in France by D. Koechlin, whose patterns had been shown to him. He also discovered the use of certain manganese compounds, which still have considerable importance as bronze dyes, greatly improved the methods of printing indigo, and made many other minor inventions. In 1825 Mercer was taken into partnership by Messrs. Fort Bros., and continued a partner of the firm until its dissolution in 1848. During this period Mercer showed great mental activity, technical discoveries of more or less importance following each other in quick succession from his laboratory.
Mercer took a keen interest in theoretical chemistry, and this interest was greatly stimulated and strengthened by the influence of Dr. Lyon (now Baron) Playfair. The two men became friends in 1841, Playfair being then one of the chemists at Messrs. Thompson's works at Clitheroe. Playfair and a few scientific friends met once a week at Whalley to discuss scientific matters; and it was at one of the Whalley meetings that Mercer propounded the first rational theory of the so-called ‘catalytic’ action. He read a paper on the subject at the Manchester meeting of the British Association in 1842; and the theory was more fully developed and illustrated by Playfair (Mem. Chem. Soc. iii. 348). Certain observations of his made in 1843, and discussed at the Whalley meetings, led Playfair to the discovery of a new class of compounds, the nitro-prussides. In 1847 Mercer joined the Chemical Society (ib. iii. 315). In 1848 the Oakenshaw firm decided to dissolve partnership and retire, rather than face the severe competition which had arisen among calico-printers—their determination proceeding chiefly from an unwillingness to manufacture goods of an inferior quality at a cheaper rate. The profits of the undertaking had been considerable, and Mercer was now free to pursue researches sketched out during the busy years. He undertook an investigation on the action of caustic soda, sulphuric acid, and zinc chloride on cotton-cloth, paper, and other materials made from vegetable fibre. These experiments (which were carried out in commercial partnership with Robert Hargreaves of Broadoak, near Accrington, and at his works) led to the discovery of the process known as ‘mercerising,’ and to the preparation of parchment paper, patented by Mercer in 1850. By treating cotton-cloth with any one of the reagents mentioned, in a solution of a certain concentration, the individual cotton fibres become thicker and shorter, and the ​strength of the cloth is greatly increased. It also becomes semi-transparent, and dyes far more rapidly than ordinary cloth, this being due to the swelling up of the cell-walls in the fibre (Crum). Owing to the expense of the treatment, the use of mercerised cloth has been hitherto limited to special applications, e.g. the manufacture of ‘calico-printers' blankets,’ in which increased strength of the fabric is required. In 1851 Mercer, who was one of the jurors of the International Exhibition held in London in that year, and therefore excluded from the ordinary distinctions, was awarded a council medal for the discovery of mercerisation. In 1852 he reluctantly assented to becoming a fellow of the Royal Society. In 1858 he contributed a paper to the meeting of the British Association at Leeds on the reducing action of light on persalts of iron, and their subsequent treatment with potassium ferricyanide, which yields a blue colour, varying in depth according to the intensity of light to which they have been exposed. The experiments were originally made by Mercer in 1828, and had been rediscovered by Robert Hunt [q. v.] The discovery of this photo-chemical action has given rise to many technical applications; Mercer himself proposed to utilise it for recording the intensity of sunlight, and Jordan has since practically carried out this suggestion in an instrument at present employed in meteorological observatories. At the Leeds meeting of the British Association Mercer also read a paper ‘On Relations among the Atomic Weights of the Elements;’ but he did not succeed in obtaining any results of importance in a field which has since proved fertile in discoveries. In 1859 his wife died, and from this time forward Mercer seems to have given up his scientific work. In 1861 he was placed on the commission of the peace for the county of Lancaster, but was judged by those who knew him to be too merciful for a magistrate (Parnell, Life, p. 266). In 1862 he served as a juror for the second international exhibition. A severe cold, brought on by falling into a water-reservoir in 1864, was the cause of a painful disease, of which Mercer died on 30 Nov. 1866. He left behind him two sons and two daughters.
In his private life Mercer was eminently unselfish and lovable. Endowed with the perseverance and business capacity necessary to raise himself from poverty to affluence, he was never grasping; and although he patented some of his inventions, he freely gave away many others, which brought large sums of money to those who profited by them. Through life he took an anxious interest in religion and religious affairs. In 1849 he seceded from the Wesleyans and returned to the established church, but, with characteristic liberality of mind, he continued to give material help to the local Wesleyan institutions. He was an ardent reformer, and was probably much influenced in his views by a short acquaintance with Richard Cobden [q. v.], who, with two partners, acted as the London agent for Messrs. Fort Bros. from 1828 till 1831 (J. Morley, Life of Cobden, i. 15–18). In his experimental discoveries Mercer displayed great fertility of invention and a remarkable insight into chemistry. His classical researches on catalytic action, on the constitution of the ferrocyanides and of bleaching powder, and his anticipation of Pasteur's germ theory (communicated in a letter to Playfair), show the true scientific temper. There can be no doubt that had he devoted himself entirely to research he would have been among the most distinguished chemists of the day.
Among Mercer's more important discoveries, besides those already quoted, may be mentioned: (1) the use of potassium ferricyanide and potash for the discharge of indigo (Mem. Chem. Soc. iii. 320); (2) the use of arseniates as a substitute for phosphates in the process of ‘dunging;’ (3) the treatment of woollen fabrics (delaines, &c.) with a weak oxidising agent before printing; (4) the manufacture of sodium stannate and stannite in the dry way; (5) the production of ‘sulphated oil’ for the Turkey-red process; (6) the discovery of the solubility of cellulose in ammoniacal copper solutions.
[Authorities cited; E. A. Parnell's Life and Labours of John Mercer (compiled from materials supplied by Mercer's family and revised by Lord Playfair); Journ. Chem. Soc. 1867, p. 395 (obituary notice); Report of British Association, Notices and Abstracts, 1842 p. 32, 1858 pp. 57, 59; Journal of Royal Institution, 1852; List of Fellows of the Royal Society, 1853; F. H. Bowman's Structure of the Cotton Fibre, 2nd ed. p. 52; private information from the Rev. A. F. Johnson, who kindly consulted the parish register of Great Harwood; from J. J. Hummel, esq., professor of dyeing at Yorkshire Coll., Leeds; and from E. Bentz, esq., of Owens Coll.]
P. J. H.
Dictionary of National Biography, Errata (1904), p.198 N.B.— f.e. stands for from end and l.l. for last line
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