1) With chemicals 2) With respect to chemistry 
• (adv.) According to chemical principles; by chemical process or operation.
Chem'ic·al·ly adverb According to chemical principles; by chemical process or operation. 
[adv] - by the use of chemicals 2. [adv] - with respect to chemistry
chemically 1. According to chemistry or its laws. 2. By a chemical process.
adverb by the use of chemicals; `chemically fertilized` adverb with respect to chemistry; `chemically different substances`