William Grapel was a barrister-at-law and collector. On 24 August 1867 he married Sarah Ann, youngest daughter of John Orford, Esq., of Brooks Hall, Ipswich. Their daughter, Alora B., was born in 1872. In 1881 he was living in the St Pancras district of London.
Grapel was called to the bar in 1853.
Whistler and Grapel were in correspondence in the late 1860s and early 1870s. Whistler promised Grapel that he might have the first opportunity to buy Nocturne in Blue and Gold: Valparaiso Bay y076 when it was finished. However, according to Edwin A. Ward it was first offered to Sir T. Sutherland for 700 guineas. Grapel also wished to buy Annabel Lee y079. However, it had been commissioned by William Graham. Whistler declared, 'I wish indeed that the little Blue Girl were yours - for you like it and I should be much gratified to see myself on your walls' (GUW #01792). Grapel also expressed an interest in purchasing Venus Rising from the Sea y093 and Violet Girl y102.
Grapel also bought the work of Alfred-Charles Foulogne (1821-1897), a pupil of Charles Gleyre.
Grapel, William, The Institutes of Justinian with the novel as to its successions, London, 1855; Grapel, W., Sources of the Roman Law; an introduction to the Institutes of Justinian, London, 1857; Foster, Joseph, Men at the Bar: a biographical hand-list of the members of the various inns of court, including Her Majesty's judges, London, 1885; Young, Andrew McLaren, Margaret F. MacDonald, Robin Spencer, and Hamish Miles, The Paintings of James McNeill Whistler, New Haven and London, 1980 .