He earned his Doctorate in Science in 1921. While in London, he was supported by the British Department of Scientific and Industrial Research with a fellowship of £250 a year. In August 1921, he returned to India and immediately joined the newly established Banaras Hindu University (BHU) as a professor of chemistry, where he remained for three years. He wrote the "‘Kulgeet’, or" University song. Justice N.H. Bhagwati, the then Vice-Chancellor of BHU said: "Many of you perhaps do not know that besides being an eminent scientist, Professor Bhatnagar was a Hindi poet of repute and that during his stay in Banaras, he composed the ‘"Kulgeet"’ of the University. Professor Bhatnagar is remembered with reverence in this University and will continue to be so until this University exists." He then moved to Lahore as a Professor of Physical Chemistry and Director of University Chemical Laboratories of the University of the Punjab. This portion of his career was the most active period of his life in original scientific work. His research interests included emulsions, colloids, and industrial chemistry, but his fundamental contributions were in the field of magneto-chemistry, the use of magnetism for the study of chemical reactions. In 1928 he and K.N. Mathur jointly developed the Bhatnagar-Mathur Magnetic Interference Balance, which was one of the most sensitive instruments at the time for measuring magnetic properties. It was exhibited at the Royal Society Soiree in 1931 and it was marketed by Messers Adam Hilger and Co, London. Shanti Swaroop Bhatnagar's first industrial problem was developing the process for converting bagasse (peelings of sugarcane) into food-cake for cattle. This was done for Sir Ganga Ram, the Grand Old Man of Punjab. He also solved industrial problems for Delhi Cloth & General Mills, J.K. Mills Ltd. of Kanpur, Ganesh Flour Mills Ltd. of Layallapur, Tata Oil Mills Ltd. of Bombay, and Steel Brothers & Co. Ltd. of London. His major innovation was an improvement of the procedure for drilling crude oil. The Attock Oil Company at Rawalpindi (representative of Messers Steel Brothers & Co London) had confronted a peculiar problem, wherein the mud used for the drilling operation was hardened upon contact with saline water, thereby clogging the drill holes.