The article is published in Curiosity magazine by Vigyan Prasar (August 2020 issue)
Acharya Prafulla Chandra Ray, a character defined by respect, indomitable courage and patriotism and most important his commitment to scientific integrity by using the best available local resources. He is known as the Father of Modern Chemistry in India, who reached a high level of perfection in his times. Ray can easily be regarded as the first Indian who started the integration process of ancient Indian Chemistry with modern sciences, a researcher who led Indians towards modern Chemistry, founder of Indian Chemical Society and a Startup entrepreneur.
Prafulla Chandra was born on August 02, 1861, in the village of Raruli-Katipara, Jessore district, presently in Bangladesh. His father Harish Chandra Ray was a zamindar who appreciated education and had built up an extensive library in home. His mother, Bhubanmohini Devi was very well educated with supporting views. This academic atmosphere at home, made a lasting impact on Ray and he was captivated towards literature and history.
After clearing the entrance examination in 1879, Prafulla Chandra took admission at Metropolitan Institution (now Vidyasagar College) founded by Pandit Iswarchandra Vidyasagar. As an external student, his Physics and Chemistry classes were held at Presidency College, Kolkata. Chemistry soon became his dearest subject and he set up a laboratory at his home to experiment. Halfway through his BA studies, he won the Gilchrist scholarship of Edinburgh University (1882). Ray completed his B. Sc. In 1885 and at the age of 26, was awarded a D. Sc. in Inorganic Chemistry (1887). He was elected the Vice-President of the Edinburgh University Chemical Society in 1887.
As a young Indian scientist, young P C Ray applied for a job at Indian Educational Service (IES) but despite of his accomplishments and recommendation letters, he remained jobless for a year. During this period he stayed with his friend, Jagdish Chandra Bose and spent his time reading chemistry literature. In those times jobs were limited and mostly reserved for British. Such was the racial discrimination in British times that he was given only a temporary appointment at Presidency College as Assistant Professor at a meagre salary of Rs. 250, an absurdly low pay for someone with his qualifications. Ray disagreed but eventually accepted the job. He moved to the Rajabazar Science College, Kolkata as the first Palit Professor of Chemistry in the year 1916 and continued his work with renewed vigour. His research activities thrived in the laboratories of the university even though the facilities were inadequate.
As a student at the University of Edinburgh, he was impressed by the scientific knowledge of ancients in the western world. This generated immense curiosity in him to explore the extensive contribution of ancient India in the field of science and technology. He studied various Indian texts of Susruta, Charaka and explored the world of Indian science developed hundreds of years ago. Acharya Prafulla Chandra Ray’s book, A History of Hindu Chemistry is a critically acclaimed treatise on Rasashastra and Ayurveda. The first volume of the book was published in 1902, and the second in 1909. The book was strong enough to attract the attention of western world towards Indian alchemy and lead to the globalization of the fundamentals of Rasashastra.
Prafulla Chandra was a synthetic Inorganic chemist with active interest in organic molecules and reactions especially to the chemistry of thio-organic compounds. His initial work which made him famous was based on the chemistry of inorganic and organic nitrites, he was regarded as “Master of Nitrites”. He continued his work on related compounds and thereon shifted to organic thio-compounds and their metal complexes. The metal which particularly fascinated him was mercury, maybe because it has extensively important role in Indian medicine system of Ayurveda.
In 1894, P C Ray began analysis of certain rare Indian minerals in his quest to discover some new element to fill the gaps in Mendeleev’s Periodic table. He soon reported the first ever synthesis of the previously unknown compound of Mercurous Nitrite Hg2(NO2)2, which he narrates in his autobiography as "the discovery of mercurous nitrite opened a new chapter in my life". This compound of mercury was a fascinating example of two relatively unstable ions combining to form a stable substance.
The formation of mercurous nitrite, Hg2(NO2)2 was an accidental discovery, while he was trying to react excess mercury with cold dilute nitric acid to synthesize mercurous and mercuric nitrates, Hg2(NO3)2 and Hg(NO3)2. During the course of reaction, he noticed the appearance of a yellow crystalline solid on the sides which on analysis revealed to be the unknown mercurous nitrite. The nitrite ion probably was the result of initial reduction of nitric acid by mercury. The pertinent point to be noted here is that stable mercury(I) complexes are very few in existence, even today, owing to the instability of mercury(I) towards disproportionation to mercury(II) and metallic mercury in solution.
This discovery was first published in the Journal of Asiatic Society of Bengal (1896), and immediately noticed by Nature magazine, which mentioned the work in its issue of May28, 1896, “A paper by Dr. P. C. Ray….. on mercurous nitrite, that is worthy of note…”.
In further course of his research, he published numerous significant research papers on nitrites and its related derivatives. This series of work by Ray and his students, led to laying the foundation of first research school of modern Chemistry in India. Now with advances in analysis techniques, the compound has now been structurally analysed using X-ray crystallography techniques (1985, 1986, 2011). As can be seen from the figure, the molecule is planar and centrosymmetric. The Hg atom is unsymmetrically bonded to nitrite ion through the two oxygen atoms, thereby forming a four membered chelate ring.The Hg-Hg bond length is 2.54 Å and the shorter and longer Hg-O distances are 2.20 Å and 2.61 Å respectively.
Figure: Molecular view of Hg2(NO2)2
Another of his major contribution was the synthesis of ammonium nitrite in pure form via double displacement between ammonium chloride and silver nitrite.
He also reported that on careful heating to 70oC in moderate vacuum, a part of the ammonium nitrite goes through the process of sublimation via vaporization. He further worked upon it to determine the vapour density of ammonium nitrite and observed that his experimental density value agreed very well with the calculated figure, thereby showing that the salt existed in ion-pair form. In those times, only ammonium chloride salt was known to exhibit this property. In 1912, he presented this work at Chemical Society, United Kingdom before a distinguished audience including Noble Laureate William Ramsay. In its issue, the Nature magazine mentioned the work as, “…a further accomplishment in determining the vapour density of this very fugitive compound.”