Hans Pirow, mining engineer, was the son of Carl Bernhard Ferdinand Pirow, medical practitioner, and his wife Henny Jasmine Marine, born Tomby. He received his school education at Potchefstroom and at the gymnasium at Itzehoe, Germany, returning to South Africa in 1911. The next year he started studying at the South African School of Mines and Technology (from 1922 the University of the Witwatersrand), qualifying as a mining engineer in 1914. For the next six years he worked underground in various gold mines on the Witwatersrand, meanwhile obtaining government certificates as a mine surveyor and mine manager. In 1919 he published his first scientific paper, 'Some geographical aspects of the development of mineral resources in South Africa' (South African Geographical Journal, 1919, Vol. 3, pp. 41-49). With the help of a government scholarship he furthermore obtained the degree Master of Science (MSc) at the University College, Johannesburg (soon to become the University of the Witwatersrand) in 1920, based on his research on the characteristics of the gold-bearing Rand Banket. His findings were published as 'Distribution of the pebbles in the Rand Banket and other features of the rock' (Transactions of the Geological Society of South Africa, 1920, Vol. 3, pp. 64-97) and are recognised as the first sedimentological observations in the Witwatersrand goldfields. He supported the deltaic theory of E.T. Mellor* for the Main Reef Leader of the East Rand and was the first to propose that the gold might have been introduced into the conglomerates by a later pulse of sedimentation than that which laid down the gravels.
From 1920 to 1923 Pirow was employed in the Department of Mines as inspector of mines in Johannesburg and Krugersdorp and at the same time conducted research for the degree Doctor of Science in Engineering (DSc Eng), which was conferred upon him by the University of the Witwatersrand in 1924. His thesis was entitled Underground conditions liable to affect the health of workers in gold mines on the Witwatersrand and he was the first mining student to obtain a DSc degree at Wits. That same year he received a scholarship to attend the Imperial College of Science and Technology in London to investigate hygiene on mines. As part of this project he visited mines also in Germany, France and Belgium.
Returning to South Africa in 1925 Pirow worked as assistant consulting engineer at Union Corporation until December 1926, when he succeeded Sir Robert N. Kotze* as government mining engineer, a position he held for 10 years. Though he was only 34 years of age when appointed to this senior position, he more than justified the faith placed in him. During 1927-1928 he also held the position of acting secretary of mines. During this period in his career he became an influential person in the mining industry. He expressed the opinion that mining to depths of 3000 meters was feasible on the Witwatersrand, a view that was unpopular at the time, but history proved him right. Among others his efforts contributed to the establishment in 1934 of the Mineral Research Laboratory (later the Government Metallurgical Laboratory) at the University of the Witwatersrand; he was appointed as a director of the South African Industrial Iron and Steel Corporation (ISCOR) for 1930-1932; and made contributions to the work of the Mining Leases Board, Government Miners' Training School, Prevention of Accidents Committee, and the Dust and Silicosis Committee. He also served on, or gave evidence before, various commissions of inquiry into the mining industry.
During this period he published several papers dealing with, among others, temperature measurements in a borehole in the Carnarvon district (with L.J. Krige; Transactions of the Geological Society of South Africa, 1923); deep level mining and high temperatures (with Dr A. Mavrogordato; Transactions of the South African Institution of Engineers, 1927), and mine ventilation and the prevention of silicosis (Journal of the Chemical, Metallurgical and Mining Society of South Africa, 1929). At the Fifteenth International Geological Congress, held in Pretoria in 1929, he presented a paper in collaboration with A.W. Rogers*, A.L. Hall* and W. Wybergh* on 'Gold resources of the Union of South Africa'.
In 1937 Pirie resigned his post to become the local manager of the Central Mining and Investment Corporation (also known as the Corner House Group) and became a director and chairman of many of its mines. He also served on various important government bodies. During his relatively short life he had a profound influence on the mining industry in South Africa.
Pirow became a member of the Chemical, Metallurgical and Mining Society of South Africa in 1919, served on its council during the nineteen-thirties, and as president for 1929/30. His presidential address dealt with 'The future of mining in South Africa' (Journal of the Chemical, Metallurgical and Mining Society of South Africa, 1929). He was a member also of the Geological Society of South Africa, serving on its council from 1921 to 1934 and as president for 1930. His presidential address was entitled 'Notes on the development of ore deposits in South Africa' (Proceedings of the Geological Society of South Africa, 1931). He was a member of the South African Association for the Advancement of Science and served on its council for 1926/7.
Pirow had an extensive knowledge of the mining industry and was an excellent administrator and a fluent speaker. Despite this he was a modest and shy person. During the early nineteen-forties he was a member of the council of the University of the Witwatersrand. He married Sibyl Cluver, with whom he had a son.