Show hard glass the subject of hard elastic clastic anu ana malleable glass is be beginning g to attract considerable attention an and has several times been referred to in our columns bome some experiment experiments a made by dr abauer in vienna have recently been made public and will no doubt prove of interest to our readers he remark remarks sat sab at the outset that the plates of gra gla glass s prepared by him hith do 1 n trally in external appearance from ordinary glass when struck they have a peculiar ring and may frequently be thrown on the ground without breaking but when they do break breau unlike other glass they break into a multitude of small fragments with very sharp cor corners ners nerg which is a great disadvantage of this glass they stand scratching well but like those made in france they break when struck hard dr bauer prepared his plates in this way an ordinary sheet of glass wash way heated until it began to bend and was then dipped into inta a bachof batir of melted paraffin at a temperature of or 1200 00 degrees C degrees rF the principal object was not to cool thet the botand hot and soft plate steadily and slowly as is usually done but to cool it suddenly to a certa certain in temperature and allow it to cool slowly if f the cooling takes placeit this mariner manner it is no longer possible to cut the glass with a diamond nd and ites it is easy to prove by the ordinary scaly scalp of hardness that its hardness harl hanl ness is greatly increased the thickness nesri of or the glas gla gia s has also lui Iri creased increased with its haidt haidi usg the ordinary glass used by bauer in his experiments was 2 2429 to 2438 which affer after hardening became 2460 t to 2463 it lt cannot be denied says bauer that this thip glass will be useful for many purposes pur pores es and also that therel there are many uses to which it cannot be bo applied on account of its breaking into such auch small pieces when it does break there are also difficulties met with in preparing this glass on a large scale espe especially bially in introducing hollow glass and large plates quickly and uniformly amly into the bath it is not oot as yet possible lo 10 explain the cause of or the glass being hardened edby by this method of cooling the phenomenon involuntarily reminds one of the well known boulogne flacks flasks and the prince rupert drops but the breaking of or tife the latter cannot be sufficiently explained since we know that this does not happen if the ends are art eaten oft off instead of being broken we Weare are ado aho remind reminda a ed that when cooled slowly the constituent s of tho the glass glas gla gia s be separate parate to a certain extent which can only be bd prevented by a rapid cooling it was formerly believed that glass klass was a perfectly homogeneous and amorphous substance in 1852 however prof lendolt ley les doit dolt proved by etching that all our ghis gluss 8 which apper apparently eny shows no signs of chrysa tali t on consists of a mixture which is I 1 in part crystalline when glass glas s is h heated aate d to fusion or even to softness 3 and then slowly cooled it easily happens that the constituents separate and form crystalline groups reaumur mad made ethis this experiment in the last century hoping to make por porcelain delain out of glass and the product wis wib called porcelain sieg wart and others a few years ago azo a s 0 although with a different view m made a de experiments on lon this change these experiments showed that this separation takes place very easily wally if the glass is slowly cooled and that sometimes the crystalline cryst aleine portion becomes visible and when this takes place the glass id 18 said tabo to be devi deyl trifled from thebo these new ex peri ments we may cori covi conclude clude that fused glass in ja a fused state borms forms a foleita tolerably bly bocog separates more or less on cooling T if it is cooled rapidly to a certain point the separation tien does noc not go so far an antl anil d the gia gla alaa glas s remains moreho more homogeneous mogene ous which may be the cause caise of im its hardness on the one handl handi hand hud aud of its peculiar way of brea breaking king klug on the other jouana of applied 1 11 chemistry ch 1 1 |