Tech Notes

Glass Properties
All Chemglass brand glassware meets ASTM specification E438, Type 1, Class A, and is made from Boroslicate 33 Expansion glass. Specifications for this glass is as follows:
Maximum Short time use temperature	500°C
Annealing Point	560°C
Softening Point	815°C
Working Temperature	1270°C
Linear Coefficient of Expansion	32.5 x 10-7 / °C
Refractive Index	1.473

Round Bottom Flask Diameters
Capacity mL	Diameter mm	Capacity mL	Diameter mm
5	25	500	102
10	31	1000	130
15	35	2000	161
20	38	3000	185
25	42	5000	221
50	48	6000	236
100	60	10000	279
125	65	12000	295
200	76	22000	350
250	83	50000	457
300	87	72000	520

Standard Dimensions for Full-Length Interchangeable Taper-Ground Joints
Joint size Number	Approximate Diameter at small end mm	Approximate Length of Ground Zone mm	Diameter at large End of Ground Zone mm
7/25	5	25	7.5
10/30	7	30	10.0
12/30	9.5	30	12.5
14/35	11	35	14.5
19/38	15	38	18.8
24/40	20	40	24.0
29/42	25	42	29.2
34/45	30	45	34.5
40/50	35	50	40.0
45/50	40	50	45.0
50/50	45	50	50.0
55/50	50	50	55.0
60/50	55	50	60.0
71/60	65	60	71.0
103/60	97	60	103.0

Standard Dimensions for Medium-Length Interchangeable Taper-Ground Joints
Joint size Number	Approximate Diameter at small end mm	Approximate Length of Ground Zone mm	Diameter at large End of Ground Zone mm
5/12	3.8	12	5.0
7/15	6.0	15	7.5
10/18	8.2	18	10.0
12/18	10.7	18	12.5
14/20	12.5	20	14.5
19/22	16.6	22	18.8
24/25	21.5	25	24.0
29/26	26.6	26	29.2
34/28	31.7	28	34.5
40/35	36.5	35	40.0

Standard Dimensions for Short-Length Interchangeable Taper-Ground Joints
Joint size Number	Approximate Diameter at small end mm	Approximate Length of Ground Zone mm	Diameter at large End of Ground Zone mm
7/10	6.3	10	7.0
10/10	9.0	10	10.0
14/10	13.5	10	14.5
24/12	22.8	12	24.0
29/12	28.0	12	29.2
34/12	33.3	12	34.5
40/12	38.8	12	40.0
45/12	43.8	12	45.0
50/12	48.8	12	50.0
55/12	53.8	12	55.0
60/12	58.8	12	60.0
71/15	69.5	15	71.0