130 ANNUAL OF SCIENTIFIC DISCOVERY. 



formed, and no more of it is produced on further addition of a 

 drop of acid. The liquid is now repeatedly washed with water, 

 every time refreshed after a good stirriu"^, until the water does 

 not exhibit any more aeid reaction. Tiie precipitate is next 

 brought upon a cloth filter, ami, after all the water has run oil, 

 the syrupy mass is lit for use. This thickest magma is painted 

 over the iron with a brush; if it hai)pens to be too stiff, it is di- 

 luted with oil of turpentine. Immediately afterward this i);iint 

 is burnt in l)y a gentle heat, and, alter cockling, the black surface 

 is rubbed with a piece of woollen stuff dipped in linseed oil. Ac- 

 cording to M. Weiskopf, the discoverer, the varnish is not a sim- 

 ple covering of the surface, but it is chemically combined wi:h 

 the metal, and does not wear off' or peel off", as other paints and 

 varnishes do. 



Cast-iron Tubes are now made for water or gas in England, by 

 turning oft' one end conically, and boring out the end of the 

 tube to which it is to be united at the same angle, so that the 

 end of one tube may be inserted into the other without the addi- 

 tion of the ordinary cement. The junction is effected veiy 

 quickly, and the joint is perfectly tight. Piixes 3G inches in diam- 

 eter have been perfectly joined in this way. Liverpool has about 

 90 miles of gas-pipe joined in this way, and the leakage is said to 

 be much less than in other cities. 



A Cement for Leather is made by mixing 10 parts of sulphide of 

 carbon with one of oil of turpentine, and then adding enough gut- 

 ta-percha to make a tough, quickly-flowing liquid. One essential 

 prerequisite to a thorough union of the parts consists in freedom 

 of the surfaces to be joined from grease. This may be accom- 

 2)lished by laying on a hot cloth, and applying a hot iron for a time ; 

 the cement is then applied to i)oth pieces, the surfaces brought in 

 contact, and pressure applied until the joint is dry. 



Seaweed Charcoal. — This material, which is prepared from the 

 fine tangle of the Hebrides, is being extensively used in England, 

 as a substitute for animal charcoal, as a filtering medium for 

 water, for deodorizing sewage, clearing white glass, removing 

 acidity from, and decolorizing, wines, and precipitating and 

 decolorizing vegetable alkaloids. — Chem. News. 



Cement for Stone. — It is stated that an admirable cement is 

 obtained by mixing infusorial silica, such as constitutes the 

 diatoms, for instance, tripoli, with the following substances: The 

 infusorial silica is mixed in about equal proportions with oxide of 

 lead; about half a part of freshly slakrd lime is then added, and 

 the whole is made into a paste, with boiled linseed oil. This is 

 especially recommended for securing iron work in marble and 

 other stone. 



Coke. — The importance of obtaining coke, free from sulphur, 

 cannot, especially lor iron manufacture, be over-estimated. Nu- 

 merous experiments have, from time to time, been made, with a 

 view to the use of coal in which some pyrites occur, in the manu- 

 facture of a pure coke for the blast furnace. Some experiments 

 have been made in France which are stated to have been remark- 

 ably successful. The coke, when at a temperature of 300° Cent., 



