Grade and specification, not just name
The same chemical exists in technical, LR and AR grades at very different prices and for very different uses, and supplying the wrong one is a batch failure at the customer's end. Grade, concentration and packing belong on the item and print on the invoice, because that is what their quality department will check the delivery against.
Batch numbers and traceability
When a customer reports a problem, the first question is which batch. Recording batch on purchase and on sale means you can trace a complaint back to a supplier lot and forward to every customer who received it. That is not optional record-keeping in this trade — it is the difference between a contained issue and an unquantifiable one.
Returnable drums and carboys
Containers frequently go out against a deposit and are expected back, which makes them a returnable item rather than part of the sale. Recording the deposit against the party and the container as issued means you know how many are out and with whom. Shops that treat them as consumed lose a steadily growing number nobody can account for.
Industrial accounts and documentation
Your buyer is a manufacturer with a purchasing process, so the invoice needs their GSTIN, a purchase order reference, HSN codes and line-wise tax before it will be cleared. The delivery record with the vehicle and receiver reconciles against their gate register. Both come from the item and party records rather than being assembled per bill.