10-fold Improvement in exothermic reaction detection with ''ARC'' ??!

Posted on 11/03/2013

The word ''ARC'' in the context of adiabatic calorimetry refers to a technique developed over 30 years ago by Dow Chemical Company and the commercial instrument that resulted from this was the ''ARC''. That instrument long ceased to be produced but a couple of suppliers continue to use the same name for totally new instruments.  (HEL's version of the equivalent instrument is the Phi-Tec I).

One company that still uses the name ''ARC'' for a totally new device have recently claimed that their instrument can detect exothermic rates 10 to 20 times lower than the historically accepted value of 0.02 C/minute - ie that self-heat rates down to 0.001 to 0.002 C/minute can be reliably detected by their  ''es'' (enhanced sensitivity) ARC. They have very sensibly used 20%wt DTBP as the reference reaction to demonstrate this capability and their data is reproduced below:


DATA FOR 20% DTBP FROM `es ARC'

 

TEMP

MEASURED RATE (C/min)

CALCULATED RATE (C/min)

100

0.0000

0.0000

101

0.0000

0.0000

102

0.0000

0.0000

103

0.00002

-0.001

104

0.00008

0.000

105

0.00035

0.000

106

0.0010

0.001

107

0.0019*

0.001*

Based on this, they claim the exotherm is reliably detected at a self-heat rate of 0.001 to 0.0019 C/minute, when the sample temperature is 107C.  According to the supporting description, this ''ARC'' can detect events at least an order of magnitude more sensitively than other former and current 'ARC-type' devices.

This is a bold claim but one that totally ignores the results reported for the same DTBP reaction for over 30 years, which shows that the exotherm can be detected at between 110 and 120C, so typically around 115C. This detection temperature is based on the widely accepted sensitivity of 0.02C/minute.

Therefore, if the ''es ARC'' is indeed 10-times more sensitive, the DTBP reaction would be detected around 30-40C lower than historical data (ie reaction should be detected at near 75-85C, based on common extrapolation methods). Compare this with the 'es-ARC' which gives a detection temperature not even 10C better than data in 30-year old literature.

Hence, the 'es-ARC' shows no improvement worth mentioning and the ''enhancement'' claim is without foundation.



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