Use a Melting Point Apparatus to Figure Out Eutectic Point

Melting point apparatus  is an instrument used to measure melting point of substance. In this experiment, we were going to measure the melting points of different components, and figure out the eutectic point by using polynomial fitting.

Fisher-Johns apparatus

Observing through the lens

Melting point apparatus

Experimental record

Component	Melting range (℃)	Average (℃)
100% Benzoic acid	122.0~124.0	123.0
99% Benzoic acid + 1%  2-naphthol	118.0~120.0	119.0
80% Benzoic acid + 20%  2-naphthol	90.4~113.6	102.0
50% Benzoic acid + 50%  2-naphthol	90.2~106.5	98.4
20% Benzoic acid + 80%  2-naphthol	88.3~105.8	97.1
100% 2-naphthol	120.0~122.0	121.0

Data processing

Model	Polynomial
Adj. R-Square	0.91129	0.99865	0.98503
		Value	Standard Error
Poly. fitting of Max.	Intercept	122.42316	1.75243
Poly. fitting of Max.	B1	-70.83259	42.35292
Poly. fitting of Max.	B2	179.32579	205.90115
Poly. fitting of Max.	B3	-294.68184	325.2792
Poly. fitting of Max.	B4	185.78141	161.53845
Poly. fitting of Min.	Intercept	121.58944	0.45627
Poly. fitting of Min.	B1	-325.07157	11.02727
Poly. fitting of Min.	B2	1139.85131	53.6097
Poly. fitting of Min.	B3	-1644.22212	84.69171
Poly. fitting of Min.	B4	827.85708	42.05916
Poly. of average	Intercept	122.00714	1.10342
Poly. of average	B1	-198.13952	26.66762
Poly. of average	B2	660.78879	129.64618
Poly. of average	B3	-970.95412	204.81286
Poly. of average	B4	507.30774	101.71309

Analysis

Poly. of average	F(x) = y = 122.00714-198.13952*x+660.78879*x^2 -970.95412*x^3+507.30774*x^4
First order derivative of F(x)	y’ = -198.13952+1321.57758*x -2912.86236*x^2+2029.23096*x^3
Eutectic point (Benzoic acid / Total)	0.717
Eutectic temperature (℃)	95.8