Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
EMERSON ELECTRIC CO
   2. Issuer Name and Ticker or Trading Symbol
MKS INSTRUMENTS INC [MKSI] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
8000 W. FLORISSANT AVE.		 3. Date of Earliest Transaction (Month/Day/Year)
04/21/2006
(Street)

ST LOUIS, MO 63136		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 04/21/2006   S   15,000 D $ 24.2383 (1) 7,251,711 I Through a subsidiary (2)
Common Stock 04/24/2006   S   15,000 D $ 24.1183 (3) (4) 7,236,711 I Through a subsidiary (2)
Common Stock               1,065,182 D (5)  

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
EMERSON ELECTRIC CO
8000 W. FLORISSANT AVE.
ST LOUIS, MO 63136		     X    
ASTEC AMERICA INC
5810 VAN ALLEN WAY
CARLSBAD, CA 92008		     X    

Signatures

 /s/ Harley M. Smith, Assistant Secretary for Emerson Electric Co.   04/25/2006
**Signature of Reporting Person Date
 /s/ Harley M. Smith, Secretary for Astec America Inc.   04/25/2006
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) The sales were effected in multiple transactions, at varying prices, on April 21, 2006, as follows: 1,600 shares at $24.00; 200 at $24.14; 100 at $24.15; 230 at $24.17; 2,200 at $24.18; 270 at $24.19; 1,701 at $24.20; 800 at $24.21; 600 at $24.22; 100 at $24.24; 899 at $24.25; 700 at $24.26; 1,274 at $24.27; 600 at $24.28; 126 at $24.29; 200 at $24.30; 400 at $24.31; 594 at $24.38; 106 at $24.39; 1,200 at $24.40; 200 at $24.41; 100 at $24.42; 200 at $24.43; 100 at $24.44; 200 at $24.46; 100 at $24.47; and 200 at $24.51. The weighted average sales price for these transactions was $24.2383 per share.
(2) The reported securities are owned directly by Astec America Inc. The Reporting Person is the ultimate parent company of Astec America Inc.
(3) The sales were effected in multiple transactions, at varying prices, on April 24, 2006, as follows and as described in Footnote 4 below: 200 shares at $23.87; 200 at $23.91; 400 at $23.92; 200 at $23.93; 200 at $23.95; 500 at $23.96; 800 at $23.97; 300 at $23.99; 600 at $24.00; 800 at $24.01; 500 at $24.02; 400 at $24.03; 200 at $24.04; 400 at $24.05; 200 at $24.06; 400 at $24.07; 400 at $24.08; 200 at $24.09; 200 at $24.10; 200 at $24.11; 200 at $24.12; 200 at $24.13; and 400 at $24.14.
(4) This footnote sets forth additional detail with respect to the transactions described in Footnote 3, as follows: 400 shares at $24.16; 192 at $24.17; 300 at $24.18; 408 at $24.19; 100 at $24.20; 800 at $24.21; 200 at $24.22; 500 at $24.23; 800 at $24.24; 1,400 at $24.25; 300 at $24.26; 600 at $24.27; 200 at $24.28; 200 at $24.29; 300 at $24.30; and 200 at $24.32. The weighted average sales price for these transactions was $24.1183 per share.
(5) The reported securities are owned directly by Emerson Electric Co.
 
Remarks:
See Exhibit 99.1 - Joint Filer Information

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