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        <link:definition>995635 - Disclosure - Goodwill (Tables)</link:definition>
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        <link:definition>995655 - Disclosure - Pension and Post-Employment Benefits (Tables)</link:definition>
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        <link:definition>995665 - Disclosure - Income Taxes (Tables)</link:definition>
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        <link:definition>995685 - Disclosure - Fair Value Measurements (Tables)</link:definition>
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        <link:definition>995705 - Disclosure - Reclassifications out of Accumulated Other Comprehensive Loss (Tables)</link:definition>
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        <link:definition>995715 - Disclosure - Segment Reporting - Segment Reporting (Detail)</link:definition>
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        <link:definition>995725 - Disclosure - Earnings Per Share - Additional Information (Detail)</link:definition>
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        <link:definition>995745 - Disclosure - Goodwill - Additional Information (Detail)</link:definition>
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        <link:definition>995755 - Disclosure - Goodwill - Summary of Goodwill (Detail)</link:definition>
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        <link:definition>995765 - Disclosure - Other Intangible Assets - Summary of Other Intangible Assets (Detail)</link:definition>
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        <link:definition>995785 - Disclosure - Pension and Post-Employment Benefits - Additional Information (Detail)</link:definition>
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        <link:definition>995795 - Disclosure - Pension and Post-Employment Benefits - Plan Net Pension Credit (Detail)</link:definition>
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        <link:definition>995805 - Disclosure - Income Taxes - Roll-forward of Unrecognized Tax Benefits and Associated Accrued Interest and Penalties (Detail)</link:definition>
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        <link:definition>995815 - Disclosure - Income Taxes - Additional Information (Detail)</link:definition>
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        <link:definition>995825 - Disclosure - Long-Term Debt - Additional Information (Detail)</link:definition>
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  <xsd:element id="iosp_UnrecognizedTaxBenefitsIncreaseDueToInterestAccrual" name="UnrecognizedTaxBenefitsIncreaseDueToInterestAccrual" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="iosp_RemediationMember" name="RemediationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
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