Keywords: THC 2003.902.069 Colorimeter for NO2 Analysis.tif Photograph unknown en Colorimeter for nitrogen dioxide analysis NO2 depicted people depicted place Fixed Nitrogen Research Laboratory ca 1920 1950 Print Photographic Original Negative in 4 5 Institution Chemical Heritage Foundation object history Travis Hignett Collection The images are from the United States Department of Agriculture U S D A Fixed Nitrogen Research Laboratory F N R L and date from the 1920s-1950s Many of the images are mounted on scrapbook pages and were originally in scrapbook albums exhibition history credit line Gift of Travis Hignett CHF Collections Image downloaded with permission from the Chemical Heritage Foundation as part of the Wikipedian in Residence initiative accession number 2003 902 069 http //www chemheritage org/discover/collections/collection-items/photographs/colorimeter-for-nitrogen-dioxide-analysis-fixed-nitrogen-research-laboratory aspx Chemical Heritage Foundation CHF-cooperation PD-USGov Images from the Chemical Heritage Foundation Images from the Travis Hignett Collection Fixed Nitrogen Research Laboratory Laboratories in the United States Colorimeters Scientific instruments |