A nalyses of Boohs . 63 



with tlie solution of iron alum, No. I. Dark logwood 

 black is produced with the acetate of iron mordant, No. 2. 

 Logwood colours do not stand stronger iron mordants. 



The mordanted cloth, as with all colours which have 

 iron for their base, is purified in the cow-dung bath. To 

 form the dark logwood black, 4 lbs. of mordanted cloth are 

 required for 1 lb. of logwood. 



Dyeing. — For this purpose a decoction of logwood is em- 

 ployed, which is rendered lukewarm by the addition of 

 cold water. The cloth should be dyed in this, but the so- 

 lution should not be boiled. 



The black acquires, by hot soap-suds, a deep velvet 

 lustre. 



Properties of logwood black, — This colour, when it is 

 formed with not too much iron mordant, is very permanent, 

 while light, air and washing with soap have but little, 

 action on it. 



Lime water, ammonia and vinegar have no injurious action. 



Lime juice produces a slight spot which ammonia com- 

 pletely removes. 



Solution of potash changes the logwood black most. It 

 makes a brownish yellow spot which completely disappears 

 by immersion in vinegar. 



Tin mordants. No. 1 and 2, printed on it in a stronger 

 solution discharge a violet colour. 



{To he continued.) 



Ayticle XI. 



ANALYSES OF BOOKS. 



Narrative of an Excursion to the Lake Amsanctiis and to Mount 

 Vultur in Apidia. By Charles Daubeny, M.D. F.R.S., &c. 



{Read to the Ashmolean Society.) 



The localities to which this tour refers are situated in the midst of 

 volcanoes, which have been comparatively in recent action. The 

 author has devoted much time to the careful investigation of the 

 chemical products of volcanoes, and on the present occasion these 

 have not been forgot. He compares Lagoni with Amsanctus. " At 

 the Lagoni we see pools of water in a state of absolute ebullition, from 

 the quantity of steam which is constantly rising through them, and 

 which imparts to them a temperature exceeding 180° of Fahrenheit. 

 This steam seems to carry up with it boracic acid and sal ammoniac ; 

 the former in sufficient quantities to make it worth while to evapo* 



