The number of H-1B visas awarded to researchers in the chemical sciences is already extremely low. In 2015, according to data from the U.S. Citizenship & Immigration Services, initial H-1B petitions approved in occupations in mathematics and physical and life sciences accounted for approximately 4% of the total approved H-1B petitions. In comparison, 62% of the approved H-1B petitions went to computer-related occupations.I can't quite tell the accuracy of "myvisajobs.com", but I presume their database is based on Department of Homeland Security data. In the 2015 database, the number of Labor Condition Applications for chemists was 2,180, with an average salary of $63,669. By comparison, the number of chemists in the US workforce is estimated by the Bureau of Labor Statistics is around 91,100.
*Full disclosure: my editor.