Chemical, Glassware and Instrument Evaluation Checklist

I listed some pointers to follow in selecting glassware, equipment, chemical reagents, chemical preservatives or natural ingredients offered by several manufacturers.

test tubes wooden spoons glass jars strainerFirst and foremost is the quality. Is the glassware made of strong borosilicate glass? Is the chemical reagent/preservative of high purity. Is the equipment durable, dependable and give accurate results. If the answer is yes, then include it to your list of candidates.

Second is the pricing. The reagent might be of high purity but it will take gold in exchange. Most of the time an average cost equipment will do the same or even better than more expensive brands.

Availability. Consider the time and effort that will be spent to get the product close to you. An imported versus locally made. An in-town versus out-of-town. Sometimes it is cheaper to buy more expensive product from local stores. A certain product become more expensive as it travels.

Exchange policy. Is the merchant willing to replace defective products? Make this matter clear beforehand. Any defective item that cannot be exchanged are losses.

Service warranty. Is the supplier willing to repair the equipment in case of incidental failures. Know their terms well cause some might have hidden policies that might make you scratch your head.

I was tired of evaluating 30 items offered by different suppliers. I took a short break and wrote this.

Glassware Taper Joint Measurement

Years of work outside laboratory environment seemed made me clueless about many simple laboratory terms and methods. I think I have forgotten many important rules and protocols. I feel that I am not fit for this kind of work anymore. I wish my doubt is not true.

I need to order three flat bottom boiling flask as replacement part for traditional Soxhlet Extraction System – an equipment to measure crude fat or simply oil content.

The problem! I forgot how to measure the glass standard taper joint, the ground inner/outside finish for easily connecting glasswares together. The joint size is usually permanently written on surface but I cannot find it anywhere.  Or, maybe I never knew how to measure it from the very start. I was absent when our Chemistry professor discussed it.

At times like this, back reading is my best friend.

Glassware standard taper joint looks like this.

flat bottom flask ground jointAfter reviewing few paragraphs: The size is expressed by two numbers separated by forward slash. The joint size 19/22 means 19 mm width of the joint widest portion and 22 mm taper length. Get outside width  for male joint and inner for female socket.

It is recommended to use vernier caliper for accurate measurement. Search for matching product on-line or on catalog books. If no similar products are found, then it is probably out of stock or you have made a wrong measurement.

vernier caliper soxhlet and flask