CHEMICAL SCIENCE. 323 



212 degrees Fahr., to drive off nil the moisture and to harden the clay. 

 When this is accomplished, the ferric pencil or tracer is removed from the 

 oven or other place, and plunged into molten bees-wax, spermaceti, or any 

 substance of similar character, which -\vill form an air-tight coating, and not 

 decompose) t'.ic ferric salt. The chemical pencil or tracer, thus produced, 

 may be placed between strips of wood, like a common lead pencil, or it may 

 be placed in a metal pencil-case, and the point of it scraped to expose it to 

 the f;i;\ The chemically-prepared paper, previously described, is now traced, 

 pressed, or written upon with the pencil or instrument described. The 

 ferric salt in the said pencil, during the act of writing, when exposed to the 

 atmosphere, absorbs moisture ; and when it (the ferric salt) comes in contact 

 with the salt or substance in the prepared paper, the salts or substances in 

 the pencil and paper unite chemically (forming double decomposition), pro- 

 ducing a new feme compound in the prepared paper, and thereby producing 

 chemical-colored characters, marks, or writing. Any of the ferric salts 

 named for the pencil will produce the different colors mentioned on paper 

 prepared with the substances heretofore specified for producing these colors. 

 The pencil or tracer may also be made of a very porous substance, which 

 may be steeped in a solution of ferric salt, then dried to expel the moisture, 

 leaving the salts in fine crystals in its pores ; it is then plunged into bees- 

 Avax, as described, for the above-described pencil, and for the same purpose. 

 Type may be formed in the same manner as the ferric clay pencil described, 

 and chemical printing may be executed without the use of common topical 

 ink, which in some cases may be advantageous. A very porous fountain 

 pencil may also be made, one whose pores will permit fine ferric salt to per- 

 colate as it were through them, and be transmitted to the paper in the act of 

 tracing or writing, and impressed on the paper by a hard point on the pencil, 

 to bring the salt or salts in the pencil and prepared paper into contact, when 

 the two will unite under hygroscopic conditions of the ferric salt, and pro- 

 duce the chemical marks and writing heretofore described. 



Another method of obtaining the hygroscopic condition necessary to form 

 a chemical union between the salt or substance in chemically-prepared paper 

 and a pencil, without employing a deliquescent salt to produce chemical 

 writing on paper, is to use glycerine as a component part of the chemical 

 pencil or marker. Without the employment of a solution it will afford the 

 same requisite amount of moisture as a deliquescent salt. Paper prepared 

 with starch, as a sizing, will produce blue marks or writing, if it be traced 

 upon with a porous pencil or fountain pencil containing iodine and glyce- 

 rine the latter not being present as a liquid, but simply as a hygroscopic 



agent. 



Another method of producing the same chemical marks or writing on 

 paper as those described is, to prepare the paper in the same manner as that 

 first described, and employ a dry salt in the pencil, and supply the hygros- 

 copic conditions necessary to form the chemical union of the chemically-pre- 

 pared paper and pencil during the act of writing or tracing, by placing a 

 moist sheet of paper under the paper to be written upon ; or they may be 

 supplied, after tracing or writing, by pressing a sheet of moistened paper on 



