December 14th, 2016, 09:18 PM  #1 
Member Joined: Oct 2016 From: labenon Posts: 33 Thanks: 4  Brix Calculations
Can any one help me to solve this? I have been working on my spreadsheets and have reached a confusing cross road intersection regarding Brix calculation. This because there seems to be more than one way of calculating it with a resulting different answer. Method 1. Calculating °Brix from SG is based on an expression from a polynomial fit to a large data set: brix = 143.254 * sg3  648.670 * sg2 + 1125.805 * sg  620.389 Method 2. Brix = (((182.4601 * SG 775.6821) * SG +1262.7794) * SG 669.5622) The error is in the decimals, though it may appear insignificant it has implications in other calculations which are derived from the Brix answer. I am getting confuse with decimals. 
December 14th, 2016, 09:38 PM  #2 
Senior Member Joined: Sep 2015 From: USA Posts: 1,653 Thanks: 840 
the two expressions are significantly different I've seen the idea behind method 2 used to reduce numerical error in evaluating polynomials but the numbers don't match up with the polynomial in method 1. what method two should look like is $Brix =((143.254 \text{sg}648.67) \text{sg}+1125.81) \text{sg}620.389$ 
December 19th, 2016, 09:38 PM  #3  
Member Joined: Oct 2016 From: labenon Posts: 33 Thanks: 4  Brix Calculations Quote:
 
December 20th, 2016, 10:34 PM  #4 
Senior Member Joined: Sep 2015 From: USA Posts: 1,653 Thanks: 840  
December 21st, 2016, 09:49 PM  #5  
Newbie Joined: Dec 2016 From: United Kingdom Posts: 14 Thanks: 1  Brix Calclation Quote:
Hi, You can use this formula. °Bx = (((182.4601*S 775.6821)*S +1262.7794)*S 669.5622) Or I have also found this information, I hope it will help you somehow! The Brix value can be obtained from the polynomial fit to the ICUMSA table: Bx = (((((11758.74*nD 88885.21)*nD + 270177.93)*nD  413145.80)*nD + 318417.95)*nD 99127.4536) where nD is the refractive index, measured at the wavelength of the sodium D line (589.3 nm) at 20 °C`  

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