Carbon and Sulfur Determination in Soda-Lime Glass (CS744)

Importance of the Topic

Accurate determination of sulfur and carbon content in soda-lime glass is critical for controlling color, bubble removal efficiency and mechanical properties. Sulfate and sulfide additives influence redox state, melt homogeneity and final product quality. Routine, precise analysis enables manufacturers to optimize batch formulations, ensure product consistency and meet regulatory standards.

Objectives and Study Overview

This application note describes a rapid, reliable method for quantifying total sulfur and carbon in soda-lime glass using the LECO CS744 induction furnace analyzer. The study aims to establish sample preparation procedures, instrument settings, calibration protocols and typical performance metrics to support quality control in glass production.

Instrumentation Used

• LECO CS744 Series Carbon and Sulfur Determinator with induction furnace
• Ceramic crucibles (528-018 or 528-018HP), baked at 1000–1250 °C
• LECOCEL II accelerator and Iron Chip accelerator
• Reference materials: LECO LCRM®, LRM®, NIST SRM 80a, NIST SRM 92

Methodology

Sample preparation requires a representative, homogenized glass powder weighed at ~0.25 g into pre-baked crucibles. Accelerators are layered on top of sample or standard. Analysis proceeds in three phases: blank determination, calibration/drift correction, and sample measurement. Key instrument parameters include:

• Purge time: 15 s; analysis time: 20 s; sample cool time: 10 s
• Furnace power: 100%
• Nominal mass: 1.0000 g
• Carbon integration time: 50 s; sulfur integration time: 55 s

The procedure follows these steps:

1. Instrument warm-up and conditioning with matrix samples (three replicates)
2. Blank measurement with three replicates of LECOCEL II and Iron Chip accelerators
3. Calibration/drift correction using three replicates of each reference material
4. Sample analysis with desired replicate count

Main Findings and Discussion

Typical results demonstrate high accuracy and precision:

• NIST SRM 80a (beads): sulfur average 0.084 %, standard deviation 0.0006%
• NIST SRM 92 (powder): sulfur average 0.015 %, standard deviation 0.0013%

Results confirm linear calibration through origin using synthetic certified reference material. Precision is sufficient for quality control thresholds in soda-lime glass production.

Benefits and Practical Applications

• Rapid turnaround (under one minute per analysis) supports high-throughput environments
• Minimal sample preparation with standard accelerators and crucibles
• Reliable control of glass color and bubble content through accurate sulfur measurement
• Compliance with industry and regulatory quality standards

Future Trends and Opportunities

Advancements may include automation of sample handling, integration with LIMS for real-time monitoring, and expansion to other glass types. Emerging sensor technologies and machine learning models could further refine process control and predictive maintenance.

Conclusion

The LECO CS744 method provides a robust, efficient solution for simultaneous carbon and sulfur determination in soda-lime glass. Its high precision, rapid analysis time and straightforward workflow make it ideal for production laboratories and quality control departments.

Reference

• LECO Corporation. Carbon and Sulfur Determination in Soda-Lime Glass. Inorganic Application Note, 2018.
• LECO CS744 Series Operator’s Instruction Manual.
• NIST SRM 80a and NIST SRM 92 Certificates of Analysis.