From Heinrich Debus   Octbr 23rd 60.

Queenwood College | Stockbridge | Oct[o]b[e]r 23^rd 60.

My dear John,

I was very much pleased with the letter I received from you this morning.¹ As I have a little time to spare I will answer to day one of your questions.

Nitrite of ammonia or a mixture of nitrite of potash and chloride of ammonium undergoes according to condition of experiment different decompositions. Dissolved in water and heated, it is asserted that perfectly pure nitrogen and water are formed. If heated in the dry state nitrogen, nitric oxide (NO₂), nitrous oxide (NO), ammonia and water are obtained. Now I can discover no where a proof that the gas obtained from the solution is really pure nitrogen.

Knowing how much assertions of such a nature are worth I should not be content by assuming that the nitrogen prepared by boiling a solution of nitrite of potash and chloride of ammonium was pure, but experiment in the following manner.

Prepare the nitrogen by boiling a solution of nitrite of potash and chloride of ammonium. Pass this nitrogen through a tube containing pumic-stone² (Bimsstein) moistened with a solution of caustic potash, after this through a tube containing pumic-stone moistened with strong sulphuric acid, and after this through a tube 2 feet long containing red hot copper turnings.

Only after the gas has been treated thus you may be sure to have pure nitrogen.

The copper turnings are prepared for this process in the following manner: heat the commercial turnings in crucible to redness for some time; transfer the same to a glass tube of bohemian glass (of the size of a combustion tube), heat to redness and pass hydrogen over the red hot copper turnings. Thus you obtain pure metallic copper. If you like I will set Flight³ to prepare you some turnings.

As to the nitrogen of our atmosphere, pray how did you prepare it? Besides carbonic acid, ammonia and water and oxygen the air contains organic substances of a nature utterly unknown to us. All these must be removed. It may be well for chemical experiments simply to abstract the ammonia, water, oxygen and carbonic acid but for such a delicate reagent as radiant heat only a perfectly pure material will do.

Pure nitrogen may be obtained from air as follows:

Pass the air through 2 tubes, one containing pumic-stone and potash and the other pumic-stone and sulphuric acid. Here water carbonic acid and ammonia are withdrawn from it. Thus purified pass the air through a red hot tube containing bright copper turnings. The copper removes the oxygen and the high temperature destroys the organic matter. Or what is better let there be where the gas enters the tube a layer of oxide of copper of a few inches in length and after this the metallic copper. The oxide of copper burns the organic matter to carbonic acid and water. At the other end were the gas leaves the tube you have nitrogen and this water and carbonic acid. Therefore, after the passage of the gas over the oxide of copper and metallic copper let it proceed through two tubes containing potash and sulphuric acid, in order to purify it.

Gas holder with air

B empty bottle.

C pumic-stone with potash

D pumic-stone with SO₃HO⁴

E oxide of copper 6 inches long

both red hot.

F metallic copper 18 inches long

G pumic-stone with potash

H. pumic-stone with sulphuric acid

K. gas conducting tube.

The air must pass very slowly through this apparatus in order that the different reagents have sufficient time to act. It is even advisable in order to be quit sure to double the number of the tubes and the length of the layer of copper shavings.

Phosphorous does not remove the organic matter and other methods, except the one described here, to not furnish a pure nitrogen from air.

In September I bought a bottle of pale brandy; it is still corked and I suppose I must drink it myself.⁵ More in my next letter. If I can prepare anything for you I shall do so with pleasure.

Always your | H. Debus

RI MS JT/1/D/25