Exhibit 23(a)

Consent of Independent Registered Public Accounting Firm

The Board of Directors

Olin Corporation:

We consent to the use of our report dated February 27, 2017, with respect to the consolidated balance sheets of Olin Corporation and subsidiaries as of December 31, 2016 and 2015, and the related consolidated statements of operations, comprehensive income (loss), shareholders’ equity, and cash flows for each of the years in the three-year period ended December 31, 2016, and the effectiveness of internal control over financial reporting as of December 31, 2016, incorporated by reference herein and to the reference to our firm under the heading “Experts” in the prospectus.

/S/ KPMG LLP

St. Louis, Missouri

March 3, 2017