- Compliance with DIN ISO 835 standard with colour code.
- Accuracy as per Class ‘B’.
- Printed in Amber/ Blue Colour
- These pipettes are graduated for delivery from zero mark to the last graduation mark
- Color coded for each capacity making it easier to recognize
OVERVIEW:
The GWSI 25 ml Class B Mohr pipette is the teaching measuring pipette that stops above the jet. Premium borosilicate 3.3 glass gives high thermal shock resistance, hydrolytic resistance, and chemical inertness on a long 25 ml stem. Interval is 0.20 ml; Class B tolerance is ±0.20 ml to ISO 835 Type 1 — twice the Class A volumetric glassware table. Calibrated to deliver (TD) at 20 °C, **meniscus to meniscus**. Do not blow out. That last drop is not in the volume. Interchangeable ground joints stay on flasks.
HISTORY:
Students met 25 ml first as a serological and blew the tip empty. Mohr’s Type 1 25 ml was the pipette that taught the other habit: stop on a line, leave the jet wet. Class B opened that lesson to college tenders without a Class A price. GWSI Glass Lab still draws the 25 ml Class B Mohr in Ambala as autoclavable lab glass.
APPLICATIONS:
– Pharmaceutical labs: routine 25 ml takes where Class B is written, not assay Class A
– Biotech: teaching-scale media and buffer splits, wet tip
– Industrial laboratories: general 0.20 ml-step checks
– Research labs: non-critical 25 ml measuring work
– Schools, colleges, universities & educational institutes: the tender 25 ml Mohr for first volumetric practicals
– Hospital and diagnostic benches: routine measured make-up without blow-out
MANUFACTURING PROCESS:
GWSI melts high-purity borosilicate 3.3 and draws a 25 ml stem by master hand-blowing or automated tube-draw. The last 0.20 ml line is placed above the jet and blow-out rings are omitted. The blank anneals on full-length supports so a student-length tube stays straight.
TESTING PROCESS:
First inspection is manual: last line clear of the tip, 0.20 ml pitch, no rings, jet, straightness. A polarization stress test on the polariscope follows. Delivery is then checked to I.S.O. DIN (ISO 835 Type 1) on a manual or automatic stand — TD at 20 °C, two marks, **wet tip**, Class B ±0.20 ml. NABL gravimetric calibration is optional here; it is the default on our Class A Mohr line.
PRINTING PROCESS:
The 0.20 ml Mohr scale, Class B / TD / 20 °C, color code, and GWSI name are precision silk-screened with glass enamels (ceramic inks). Kiln heat drives ceramic glass fusing so the last line above the jet survives a year of student washers.
PACKAGING PROCESS:
Cosmetic sorting pulls seeds, bent stems, and any scale that runs to the tip. Pass pipettes pack in heavy-duty double-wall boxes with shock-absorbing bubble wrap, full length cradled, tips guarded, for school cartons and export from the Science City.
MAINTENANCE & SAFETY:
– Never mouth-pipette — use a filler that can lift 25 ml
– Never blow out — if the jet is empty the student overshot
– Teach mark to mark; interval is 0.20 ml; work near 20 °C
– Show the top: no double ring means Mohr, not serological
– Do not put this Class B into a Class A qualified drawer
– Wash in a 25 ml-length pipette washer
– Autoclave this autoclavable lab glass at 121 °C if the SOP allows
– Store full-length in a deep rack — a hanging 25 ml jet chips
– Cull chipped jets and worn last lines before the next practical