[NA023119], Technical Note, Thomas Alva Edison, March 24th, 1889
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Title
[NA023119], Technical Note, Thomas Alva Edison, March 24th, 1889
Editor's Notes
[draft] Caveat Phono & EL [two pages drawings probably for rounded ball repeating points followed by several pages with discussion of squirted filaments with same heading but no date] filiments for carbonization squirted through a die like Macaroni can be made very perfect with proper material. I employ pitchy asphaltic or Bituminous materials either natural or produced artificially as in the decomposition of Organic Carbonaceous Materials or Salts or Compounds by chemicals or heat to produce tary substances The various Asphaltic like materials if containing too much volitile matter such as sulpheretted or Hydrocarbons containing a relative large quantity of Hydrogen should be heated for several hours in a sand bath to drive off as far as practicable the volitile constituents and reduce the mixture to Carbon compounds with Hydrogen Sulphur or Oxygen to the minimum quantity of Hydrogen It being is nearly every case the Hydrogen combined with the Carbon that causes the Compound to fuse easily. After thus diminishing the Carbon Compounds rich in Hydrogen there will remain an Asphaltic like residue rich in Carbon & relative lean in Hydrogen– These residues are known to chemists & in commerce as pitch the pitches produced naturally as known as Asphalts, Bitumens etc These bodies can be squirted hot into filiments for Carbonization but cannot be carbonzed directly owing to their fusibility– To render them infusible while in the act of Carbonization it is essential to still further dehydrogenize ie take out some of their combined Hydrogen to that point that the resultant is still a compound of Hydrogen or Oxygen with Carbon & capable of being sisolved by some solvent when sufficient Hydrogen has been removed The final atoms are driven out of the Compound by heat leaving the filiment pure Carbon without being distorted or swelled. If the Hydrogen has not been sufficiently removed the material of the filiment will semi fuse & the gas due to decomposition will act while escaping to puff the plastic portions & thus distort & ruin the filiment.##After the filiment has been formed from plastic Bitumens these are acted up by chemical reagents which primarily tend to displace some of the Hydrogen from its combination with the Carbon. Some of the reagents not only displace Hydrogen but enter into combination by a method known to chemists as substitution, others remove no Hydrogen directly but penetrate the mass of the filiment & become active only during carbonization of the filiment to displace the Hydrogen##If the filiments are placed in Kerosene oil containing say 1/20 part of Chloride of Sulphur The Chlorine of the Compound will eliminate Hydrogen from the Bitumen, probably some of the sulphur may enter into combination or remain mechanically in the pores--the latter may be removed by weak nitric acid##The filiments may then be carbonized without distortion they should remain in the Kerosene bath 200 hours and in the nitric acid bath 5 pct nitric 95 water for 24 hours then in water for 36 hours other Reagents can be used Nitric acid 5 percent 95 water gradually increasing the strength of the acid every day for 10 days until 75 percent acid is the final result. Pentochloride of Antimony disolved in Chloride Ethyl acts similarly to Chloride of sulphur but in the case of Antimony is deposited within the pores & must be removed by Hydrochloric acid.##Chloride of Bromine [ditto] Iodine Pentachloride Molybdeum & other carriers of Chlorine or Bromine when diluted by use of proper solvents act to displace Hydrogen Sulphur also act to displace Hydrogen in the act of Carbonization the heat causes the sulphur to abstract Hydrogen##Hydrogen may be displaced from the Combination with Carbon by the use of Oxidizing agents like nitric acid as before described. Iodic acid but selecting the Oxidizing agent care should be taken that it will not oxidize the carbon itself as for instance with Hydrochlorous acid As nearly all natural Bitumens contain ash it is best to purify the pitch substance by disolving all that can be disolved by Chloroform as this solvent is the best solvent for the compounds riches in Carbon by thinning the solution in filtering most of the sh is caught by the filter paper. Ths solvent is then evaporated off or better distilled off leaving it of the same consistency as before & then in sand bath bringing it to the right constancy for the squirting press.##Another process it to act on the Bitumens by nitric acid or other oxidizing agent until enough Hydrogen has been removed to render them infusible then disolving the compounds in a proper solution filtering to remove ash & evaporate solvent down to a point where the residue is ready for squirting the filiments will dry hard & may be bent to shape of a loop etc while warm especially just after they come from the press & carbonized without distortion. Ordinary Asphalt such as Syrian or Cubian is easily dehydrogenized & rendered infusible by nitric acid The powder after washing & drying is soluable in Chlorform especially if a little methylic alcohol is added– to render the drying of the filiment slower & thus tend to prevent cracking 15 or 25 per cent of Chloral Hydrate may be added to the powder which is soluable both in Methyl Alcohol or Chloroform--##The exact nature of the reactions taking place on these Bitumens which produce compounds approach so closely to charcoal that they can only be distinguished from it by their capability of being either disolved or softened by some solvent or combination of solvents is not known by chemists, very little investigation has taken place & these are disjointed & contradictory hence no acurate statement is possible & all that I can do is to point out generally– Neither is it possible to give exact quantities or times or temperatures, as all Bitumenous residue are of very complex nature, most amorphous, change with every change of composition or conditions under which they are produced But all can be resolved by heat into compounds Richer & Richer in carbon until a point is reached where the heat must be discontinued to prevent final decomposition or carbonization, and that they are thus plastic & may be squirted into filiments and that by chemical agency which serves to remove Hydrogen be made infusible while being carbonized & that the final Hydrogen or other atom of matter combined with the Carbon is final driven of & the filiment is charcoal and that instead of acting on the squirted filimant after formation This action may take place previous to squirting but the filiments may still be squirted as the resultant compounds of the action of say Nitric acid on all the residues after driving of the most volitile constituents is the production of a compound infusible but soluable in Chloroform or mixtures of Chloroform with acid, ethers, Methyl alcohol, Hot Aniline, Nitro Benzole, Chloral Hydrate Napthaline, Anthracene##Bituminous bodies can be artificially formed from pure volitile organic materials free from ash by passing the same through Red hot tubes & condensing the residue & evaporating to a pitch which is solid like Asphalt when cold for instance Benzole gives what is known as Bitumene The residues due to the distillation of nearly every organic substance not heated beyond Carbonization gives the Bitumenous residue##All the carbons produced by this process change their resistance while giving light and although not so serious as to render the lamps unavailable for giving light commercially as against bamboo filiments it is a quality inherent in all carbon filiments & while up to the present time no attempt has been successful to prevent this change of resistance after long burning I believe I can accomplish the result by this process owing to its capability of being made in many ways & different conditions not possible with filiments from cellulose now generally used. Filiments which change in resistance very little would be of high commercial value--
Author
Date
1889-03-24
Type
Folder/Volume ID
NA023-F
Microfilm ID
99:366
Document ID
NA023119
Publisher
Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University