96 



SCIENCE-GOSSIP. 



her eggs, which vary from six to eight in number, 

 in some convenient crevice or corner. These hatch 

 out in the space of eight to fourteen days, according 

 to the season of the year, and an exceedingly 

 minute larva emerge from such. These are of a 

 white colour w-ith scaly heads furnished with two 

 smaJl antennse but no eyes, so far as I have been able 

 to trace. Their body consists of thirteen segments 

 terminating in two small hooks. They attain their 

 full growth in about twelve days, and then change 

 into chrysalides, from whence they emerge perfect 

 fleas in the course of another twelve days. 



The above facts can readily be verified by any 

 microscopist who will take the trouble to capture 

 a pair of the mature insects, and confine them in a 

 test-tube with some cotton-wool, and providing the 

 necessary food during the experiment. The tube 

 should be covered with a piece of silk or fine 

 muslin and not with a cork, as the latter prevents 

 a proper admission of air. 



The accompanj-ing sketches are from photographs 

 taken from life, and will help to make these notes 

 more intelligible. 



32, Hensloxi'e Road, Didti'ich, S.E. 



THE CHEMISTRY OF PAPER. 



By H. H. Fraxcis Hvxdman, B.Sc. 



T)APER, from whatever source it is prepared, 

 consists, fundamentally, of a substance known 

 as cellulose. This remarkable material belongs 

 to the carbohydrates, so called because they were 

 supposed to be compounds of carbon with water ; 

 sugar and starch belonging to the same class. 



Cellulose is the framework of plant-tissues. As 

 our readers, no doubt, know, plants require for life 

 carbonic acid from the air, water and small 

 quantities of mineral substances which do not 

 affect the present remarks. From the first two of 

 these, plants make cellulose, which they want, and 

 oxygen, which they excrete. 



Cellulose, however, has also been found in certain 

 low forms of animal life, so that its presence or 

 absence can no longer be considered in separating 

 the two great divisions of the organic world. 



The most superficial observation of papers as 

 they are put on the market, shows that they differ 

 very considerably in their properties ; some are 

 tough, and do not become yellow or rotten even 

 with long keeping, while others, like that used for 

 some of the London and other evening journals, 

 do not even wait to be kept to fall to pieces, but 

 have been knowm to do so on the day of issue. 



On looking closer we find that papers can be 

 roughly divided into three groups, \iz. : papers 

 principally made from : Class i, linen or cotton 

 refuse ; Class 2, celluloses derived from straw, 

 esparto grass or wood; Class 3, mechanical wood- 

 pulp. These classes are put in the order of their 

 merit. Class 3 being absolutely worthless for any 

 paper that is intended to last at all ; Class 2 is not 

 advisable for books of the slightest value, although, 

 unfortunately, many valuable books have been and 

 are still printed on this class of paper, in spite of 

 wailings from the British Museum authorities and 

 others. 



Before considering the causes of the variation 

 in the properties of different papers, it will be 

 well first to get some idea of the properties of 



the basis of all papers, i.e. cellulose itself. The 

 purest cellulose that can be bought is the best 

 chemical filtering paper, and for those who are not 

 acquainted with this, the best white cotton w^ool. 

 Good linen and cotton fabrics and the papers made 

 from scraps of these (Class i, above) contain very 

 little else than cellulose, and that little mostly 

 of a mineral nature. 



We will now suppose a few simple experiments, 

 using cotton wool or the best unsized paper. 

 When this is dipped for a few seconds into a cold 

 mixture of sulphuric acid and water, in about the 

 proportions of one to three, and is at once 

 thoroughly washed, it gives a parchment paper 

 of much the same kind as that used for tj-ing down 

 pots of preserve. If a drop of a solution of iodine 

 is put on this it will turn it blue, and it is thus 

 found to be of the same nature as starch, which 

 also gives this blue colour with iodine. Cold 

 strong nitric acid used in the same way as the 

 sulphuric gives what is known as toughened 

 paper, but which has no particular use. If, 

 instead of using these acids singly and cold, we mix 

 them and use them warm, there results a most 

 remarkable series of compounds. A mixture of 

 three parts by weight of sulphuric and one of 

 nitric acid at 50" F. gives a substance which is 

 known as cellulose hexanitrate, and which is the 

 best gun-cotton. This is quite insoluble in a 

 mixture of alcohol and ether, though they easily 

 dissolve the inferior kind of gun-cotton, consisting 

 principally of the pentanitrate. Still lower nitrates 

 are obtained by using a warmer and more dilute 

 mixture for a shorter time. 



These lower nitrates, w-hen dissolved in alcohol 

 and ether, give the solution of collodion, used for 

 many purposes, and when they are worked up with 

 camphor and other substances,' form the many 

 useful substances known as celluloid, xj-lonite, 

 etc. A still more curious use is that of spinning 

 the collodion into a continuous thread, which, 



