ComluJUon of Phofphorus m Vacuo, 27^ 



During tne concluding months of this courfe, the pupih continued to operate in the par-' 

 ticular laboratories appointed for their ufe, either in repeating the principal experiments 

 which had been exhibited in the ledlures, or in making others which had been pointed out 

 or imagined by themfelves. Their attention was principally dire£led to the application of 

 chemical knowledge to tlie progrefs of arts and manufa<i!lures. With this view they fuc- 

 ceffively prepared different kinds of foap, varnidies, and pigments, and they executed in 

 fmall the different proceflt;s of dyeing, tanning, &c. Some of the pupils attended particu- 

 larly to the experimental refearch of fubftances proper to form the oxalic acid ; others en- 

 gaged in the experimental enquiry after thofe vegetables which contain the tanning principle, 

 and might be ufed as a fubftitute for oak bark. From thefe refearches a table has been 

 formed, which is already very ample, wherein thofe vegetables which afford a precipitate 

 with the fulphate of iron alone, are diflinguifhed from thofe which afford a dcpofition with 

 the folution of glue. This table is already very interefllng ; but it may eafily be imagined 

 that it flill prefenls vacuities to be filled up by tiine and experiments. This will form the 

 object of the work of another year; and when it {hall be finifhed, we fhall haften to prefent 

 the labours of the pupils of the fchool. 



xr. ■ 



The Combiijllon of Phofphorus in the Vacuum of the AW Pump. B^ Dr. MaRTINUS- 

 Van Mar um. 



[Concluded from page Z3-.] 



i>EING defirous of afcertaining the caufe of this fingular inflammation in air fo rarefied, 

 I put, on another day, a fmall (tick of phofphorus, wrapped in the fame manner in cotton- 

 powdered with refin, under a receiver containing about four hundred cubic inches, on the 

 plate of the air puinp, in order to obferve the phenomenon with accuracy a fecond time. 

 The temperature of the place where I made the experiment was nearly the fame as on the 

 former occafion, namely 56 degrees of Fahrenheit's fcale. To obferve the degree of 

 rarefa£lion more eafily, I placed a fliort barometer gauge under the receiver. When the 

 air was rarefied fo that the mercury was fupportcd in the gauge to the height of about an 

 inch, the light began to be enlarged on the furface of the phofphorus, chiefly at the upper 

 part of the fmall cylinder. This light increafed by degrees during the fubfequent ex- 

 hauflion, and the inflammation took place when the mercury ftood at the elevation of 5 lines. 



The flame was much paler and weaker than is afforded by phofphorus when burned in an 

 atmofphcre of the ufual dtnfity. I obferved the flame to become weaker and weaker, and 

 about two minutes afterwards the phofphorus ceafed to exhibit any light. 



rV. To afcertain whether tlie cotton powdered with refin, which was wrapped round the 

 phofphorus, might be the caufe which gave place to the inflammation, I placed under the 

 fame receiver two fmall (ticks of phofphorus of the fame fize, one of which only was 

 wrapped in the powdered cotton. Thefe two fmall pieces began to fliine at the fame time, 

 when the mercury Itood at the height of about an inch in the fliort barometer gauge. 

 Ncvcrthelcfs, the piece which was furrouiided by the cotton and powdered refin alone took 

 fire when the rarcfa^ion was more advanced. 



i thea 



