Registered with the Registrar of Newspapers for India under R.N.I 53640/91

Vol. XXVIII No. 16, December 1-15, 2018

The tree that chrome replaced

Anantanarayanan Raman

Page 3Senna auriculata watercolour illustration from William Roxburgh. Note the ear-like leafy structures at the bases of compound leaves, which provide the name ‘auriculata’ to this species. William Roxburgh formally described this species studying Indian populations of Senna auriculata.

The Chromepet story (MM, November 1st) took me back to the late 1980s and early 1990s, when I used to survey this area for the environmental damage the small and large chromium-based tanneries had inflicted to the natural environment and humans. Historically, we know that the Pallavaram (which included Chromepet) area, stretching up to and a little beyond Chengalpattu, was famous for plentiful eri-s and human-made lakes. One easy outlet for the tanneries was the eri-s and lakes to dump the effluents.

In terms of science, the primary purpose of tanneries was to turn raw animal skin into usable leather. Once the skin is degreased and depilated into hide, then the tanning process leading to the production of leather starts. This process was done for ages in India, especially in the Madras region, using vegetable material. For example, the bark of Senna auriculata (previously Cassia auriculata, Fabaceae) includes certain chemicals that were used in this process. Notably populations of Senna auriculata were (I suppose they continue to be) plentifully available in and around Madras. (See the appended beautiful water-colour image of Senna auriculata from William Roxburgh volumes digitised by Royal Botanic Garden, Kew).

Eluru (referred in British-time documents as Ellore) in West Godavari was a prominent town, which produced wool-pile carpets in the 18th and 19th Centuries. The Eluru carpets, made from the fleece of native Indian sheep, were popular, matching somewhat the quality of Middle-Eastern carpets. One key reason for the establishment of this industry in Eluru, which prospered for close to 150 years, was the availability of Senna auriculata, which supplied the wool-pile carpet weavers of Eluru with necessary raw materials to remove hair from raw skins and also to dye the carpet suitably. Medieval Europeans used extracts from the bark of oak trees, instead, for this purpose.

Friedrich Knapp (Germany) and Hylten Cavalin (Sweden) first discovered that chrome (a heavy metal) could be used in tanning skin in 1858. Unfortunately both Knapp and Cavalin did not patent their finding and it was the German-American August Schultz, who patented the process in 1884 (known as the two-bath process). Saving time and money was the principal driver for the Knapp-Cavalin finding. This enabled leather production to grow into a major industry.

From here we need to read Sriram’s narrative on Chromepet.

An article in the Journal of Cleaner Production (2014) specifically speaks about the environmental problems (including human health issues) caused by injudicious use of chromium in Tamil Nadu, India.

Chromium and leather in Madras, make us remember the Central Leather Research Institute (CLRI), Madras and its beacon-light Yelavarthy Nayudamma (see

Postscript: The compound wall of the primary school I went to in Purasawalkam separated the school property (originally that of the late Kv. Al. Rm. Alagappa Chettiar) from the house of the late Sadagopachariar, the founder of the Durable Chrome Factory (DCF) in 1924. As a schoolboy, I used to see Sadagopachariar in an easy chair on his house veranda. S. Parthasarathy, a descendent of Sadagopachariar, and present director of DCF, was my high-school mate.

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