How to Use a Blowpipe for Chemical and Mineral Analysis
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How to Use a Blowpipe for Chemical and Mineral Analysis

The blowpipe has been used since the days of the ancient Egyptains to perform analysis in chemistry or minerals until 1860. It was replaced with the Bunsen burner and spectrograph in modern analysis work.

The blowpipe is used in chemical and mineral analysis is invention of the ancient Egyptians. It probably made from the stem of the papyrus plant. The Egyptians may have even covered the end of the stem with clay to protect it from the intense heat that it was capable of generating. The blowpipe still in use today is about a foot long having a right angle turn with a small nozzle with a pinhole at the tip. The other end of the blowpipe was about a quarter of an inch in diameter.

Until the invention of the Bunsen burner in 1860 this was the only way you could make a small intense flame. In its heyday the Bunsen burner was used to discover 15 elements. That begs the question, how do we use a blowpipe for chemical or mineral analysis?

In use place the larger end of the blowpipe into your mouth and you blow through it with the smaller end where it will impinge onto a small flame. For many years a candle was used for this purpose, but it was replaced by the alcohol lamp in later years. You can even direct this flow into the flame from the Bunsen burner if the amount they is entering the gas stream is cut down so the Bunsen burner shows a yellowish flame.

The most common target for this small intense flame is a rectangular block of charcoal. Before you use the block a small hollow is dug into its surface with a knife to hold the specimen to be tested.

In use, the small intense flame is directed onto the specimen lying on top of charcoal block. The intense flame from the blowpipe will also ignite the charcoal. If you are doing a blowpipe test of a substance containing metal, the metal will form a small bead on the charcoal block when it cools.

The other thing that happens is that the nonmetallic parts of the substance to a certain extent will be deposited on the surface of the charcoal block around the cavity that was dug to hold the target specimen.

For some specimens rather than using a charcoal block a block made of plaster of Paris is substituted. Use the same procedure as described above, but the plaster of Paris will not ignite. This is often used to test substances that do not contain a metallic component.

The interpretation of the test depends on your ability to recognize specific metals when you see them. The other component of this test consists of an aura that forms on the surface of the block around the metallic bead, or collects around the specimen on a plaster of Paris block.

The color or colors of the aura found on the block as well as its size will give you a basis for interpreting the test substance. Some of the older chemistry or mineralogy books describe this in detail as well as having pictures of the resulting auras.

The Bunsen burner and spectrograph have largely replaced the blowpipe in analysis. Today it is practically a lost art, but it still has a place when used in the field by an exploration geologist or prospector.

References:

Burchard, Ulrich, The History and Apparatus of Blowpipe Analysis, The Mineralogical Record,

A Brief History of Blowpipe Analysis,

Dana, James Dwight, Manual of Mineralogy, 1865, New Haven Ct.,

This is a reproduction of James Dwight Dana’s monumental “Manual of Mineralogy” and is well worth reading. The description of blowpipe analysis in its heyday is on pages 67 to 71.

 

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Comments (1)

Great to know this information about the use of blowpipe.

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